With all the recent chat on assisted belay devises I thought this was topical. I'm currently testing both AlpineUp and Click Up. So far I like them both. Far better than my experience with other "assisted locking" devices like the Mammut Smart. (The Edelrid Micro/Mega Jul also works on the same principle although I haven't used these devices) I'll update this post as I get more time with them.
Quick Initial Observations for the Devices:
Both: The BIG selling point for these devices over the other assisted braking devices is HOW the lockup of the device occurs. In all the other devices (Smart, Alpine Smart, Micro/Mega Jul etc) the biner/rope freely slide into the lockup position. What I've found is that in normal belaying, when I go to throw out slack the devices tend to lock up on their own and cause short roping etc. I typically have to hold the device (Smart) in the "open" position with my brake hand and feed the slack by pulling rope through with my free hand. This is less than ideal in my opinion. I've always "pushed" rope into my ATC etc with the brake hand while simultaneously pulling with the free hand.
With the Click/AlpineUP it's a bit different. Both devices have a spring-loaded "paddle" that holds the biner in the non-locking portion of the slot when forces on the device are low (feeding, taking in rope). Only when there's a more forceful load on the device does it "click" over to the locking position. It's pretty slick and much easier to understand when you see it (see video clips below). ONE KEY NOTE: Both Devices REQUIRE your brake hand to hold the rope for it to lock up (you do that all the time anyway right?) If the rope is not held lockup is unlikely. This is different than a GriGri which most consider pretty "hands free" (even though you really shouldn't). The best way to think of the "Ups" is a halfway point between a fully manual ATC and the nearly automatic GriGri. It feeds more like and ATC but, WITH A BRAKE HAND, will lock up ala the GriGri.
One Note: The directions mention that BOTH devices need to be used with an HMS Style carabiner with 12mm round bar stock. Climbing Technology sells one of their own (included with the alpine up) or you can buy one. I think they recommend the HMS round bar style for consistency with the belay slot lock up. Carabiners like the Gridlock of Petzl Attache 3d will likely not work well with the "Ups" - I haven't tested this personally however - I used their included HMS for my testing.
ClickUP: This is a sport climbing device for single rope use ala the GriGri. I agree with other users that it takes more force to feed rope than a simple ATC XP/Guide. Probably more like a GriGri2. It will feed best with sub 10mm ropes but is workable with a 10.2mm. I wouldn't go with anything larger. As stated above, it's a nice halfway device between the GriGri and ATC. I usually prefer to use an ATC XP/Guide for most belaying. I've had a GriGri since '92 but it always seemed like more work to "throw" rope out when the leader was clipping. That and with the GriGri and GG2 I STILL hold down the cam with my thumb when pulling slack. I just can't find a good way to give a clean and smooth belay without holding the cam. With the ClickUp I find I can give my more consistent "ATC Belay" while also having the added benefit of lockup when needed.
AlpineUp: This one is a bit more complicated and heavy than its single rope brother. It's similar in weight/bulk to a GriGri so certainly different than my ATC Guide. It's obviously designed more for half rope use. The slots are more narrow so bulky single ropes are a bit harder to work with. 8.5mm are probably IDEAL. I need more time with it though. The AlpineUp is GREAT for the half rope belay since it doesn't lock up right away. This makes feeding slack on one rope while taking it in on the other (common with half rope technique) GREAT. The AlpineUp also offers a "Guide Mode" for belaying 2nds and an optional "dynamic belay" setup that functions like a normal tube (no lockup). This will provide the more dynamic catch (rope slips through) you want on that sketchy #3 IMP.
There's not a lot of info out there on how soft the catch is with these assisted locking belay devices but I'd put them closer to a hard GriGri catch than the softer ATC catch. There's not much rope slip going on when they lock. Belay theory on dynamic catches with gloves etc is a whole other discussion of course...
Of course, no device can guarantee locking if it isn't attended. I've used gri-gris, the Alpine Smart, and the Alpine Up, and my sense is that the Alpine Up is as likely to hold an unattended fall as any of the others. Partial confirmation is provided by the following video:
Of course, no manufacturer is going to say you can do this.
Could not tell in the jerky video, can't clearly see the device. Question: Is the Alpine Up a double version of the single rope Click Up, or a totally different device by some other company? I love my Click Up, have used it since the first month they were made available online...it is truly a simple blocking belay device. I use any time before a grigri now.
The Alpine UP is the half/twin version of the single rope Click Up.
You can use it with single ropes too if they aren't too fat. The manufacturer says up to 10.5mm, but I suspect that around 10mm is the biggest for good handling. I know someone who swears by it for a 9.8mm single line. It's real forte is for half and twin ropes.
The hole just left of the carabiner in the picture allows it to be used in a non-assisted-locking-mode, as an ordinary belay plate that will slip at high loads. The hole at the top (partially hidden by the rope) allows it to be used as an autolocking upper belay device.
I'm just getting used to my Alpine Up, and yes, it chokes on even fluffy 10mm ropes. It is lovely with doubles. I have to use the modified mode for rappel because of my light weight, but it is very smooth in that set-up and still locks up well when the lever is released. Used it once to belay from above in Click-up mode, attached to my belay loop, redirected though the anchor, with doubles and lots of rope out. It kept locking up when I tried to take in rope, so I had to tie off my second and switch to standard ATC mode. Not sure if I could avoid unintended locking if I were to practice more with how I take in rope, but would probably not try this again. Will practice with a direct belay off the anchor mode if I need an autolocking set-up in the future.
My experience with the Alpine Up has been very different. I haven't had any difficulty with it locking up in any belay configuration with single ropes of 9.8mm and 10mm and mostly double 8.5's. I've tried it in the gym with fatter worn ropes and in that situation it was a total pain in the ass.
One possible explanation for my lack of lock-up issues with appropriate rope sizes is that with the Up I belay palm-up, which gives me much more ability to control half ropes independently, but which also facilitates pumping slack to the leader with all rope types and, as an additional benefit, keeps the belay and brake strand more parallel in the heat of battle and so discourages (and in my case eliminates) unwanted locking.
Palm-up belaying with an ATC-type device leads to a braking position that is not as strong as the palm-down position, but with assisted locking this doesn't matter at all since the device, rather than the hand, is doing the braking.
It is possible that most people will have to learn slightly different hand motions with assisted locking devices. Most people I see lock off an ATC every time they take in slack, and so have an ingrained reaction to drop the brake hand at the end of every take-in cycle. You don't have to do this---and shouldn't do it---with an assisted locking device, because then you'll have to unlock the device every cycle as well.