Western Mountaineering Ultralite?

Anyone have experience with the Western Mountaineering Ultralite sleeping bag?  I am looking for a new bag that is versatile and could be used for ski traverses etc.  Says it has a low limit of 14, comfort rating of 25. I was thinking I could wear down layers for colder nights.  If folks have experience with the bag let me know.

I love love love this bag. Been my primary bag for like 9 years, including sleeping in it almost every night for like 4 years while I was on the road. It’s super light, packs down real small, and I find it to be very warm for the 20deg rating. With the right clothing I’ve slept in it below zero easy and around 20 I sleep with it draped over me like a quilt because it’s so hot. I do run warm. I use it in the summer with legs out or whatever. I’ve convinced friends to buy this bag and they share my sentiments. Build quality etc the best. When this one dies I’ll buy another. 

WM makes excellent sleeping bags, and for occasional short trips in cold weather you could definitely use an Ultralite as you've suggested. Just be aware that the nylon shell is quite lightweight and isn't water-resistant. A slightly heavier bag with a more water-resistant shell would be a better choice for longer trips where you're getting condensation or frost for multiple nights in a row. But that kind of bag may be uncomfortably warm in summer.

My wife Penelope has had this bag since 2002. It's an excellent bag for summer trips. She slept in it in 2009 on our JMT trip and had no issues. She sleeps cold and this bag, with down sweater (at times) was fine even in the highest elevations of the Sierra. I think this would be a great summer bag for you, Peter. It is very light and warm and the quality cannot be beat.. 

I used a 20 degree Western Mountaineering bag for a couple of decades, for everything. It was good to about 0 F for me, although normally for serious sub freezing conditions I  slipped it inside a 1# synthetic overbag. I don't know how cold it got exactly, but I used it for winter ski tours in the Bugaboos and the Wapta Icefields, and on Mt Washington,  NH in winter. Yes you have to be careful about keeping it dry. When tenting with clients you don't get it out of the stuff sack until everyone else is settled in their own bags! Absolute zero complaints, which isn't the case with the bag I bought from "the other guys". I will be buying another one of their bags, a Summerlite I think,  before heading off for this coming summer. 

I believe the two gentleman that started the company,  Jeff and Gary IIRC, still own it. 

I have the similar Alpinlite and can't recommend it highly enough (wide version of the Ultralite, I'm not a big guy but am a side sleeper). I've put it through its paces in the Sierra and at altitude in the Mojave / Death Valley, never super subfreezing but many nights in the low 20s and it remains cozy. A few thoughts... 1) the continuous baffles took some getting used to -- useful to be able to fine-tune the down distribution between the top and bottom of the bag, but I found it prone to 'de-tuning' meaning there is always some degree of faff moving feathers around when trying to get hunkered down for the night. Then again I could just work on my lofting technique and patience. 2) Folks have already addressed water resistance, I'll add that WM has an explicit statement on why they never use water-repellent down (the technology just isn't there yet in their eyes).

It has been my go-to bag since 2007 and is still going strong. Expect the temp rating to be accurate and warmer then competitors’ 20-deg bags. I only had to replace a worn out slider a couple of years ago. 

This is so helpful.  Thank you!  What about side sleeper and adding layers to extend the range given its dimensions?  I’m 5”9 140.   Thanks again for the input!