This will only be partially helpful, but I tried on the 1st gen that my roommate was testing for R&I (or climbing). It was supposed to be a 8 or 8 1/2 and I got my 10.5 foot into them.

I'm not sure if they've changed them at all.

My roommate and I both have size 9.5 feet and fit perfectly in size 42.5 Trango S evos. He just got a pair of Radikal lites at size 9.5 and needed to add in a superfeet footbed in order to minimize his heel rise (gave him blisters). So far he's only used them for ice climbing pretty much right from the road, so we don't know much about their hiking ability. Their sole is a bit stiffer than the Trangos, and they seem less breathable. My cousin used them on a summer mountaineering trip to CO and thought they were awesome, though they were his first ever mountaineering boot so he has nothing to compare to. I love my Trangos, they've been everywhere from backpacking in central PA to Mont Blanc and Mt. Rainier in May. IMO if you can afford the Trangos/get them at a good price, I'd spring for them. But nothing can beat the price Sierra Trading Post has on the Radikal lites, and they seem to be a high quality boot for a variety of pursuits.

I've had the Radikal Lite's for about two years. For me the sizing was approximately true. They have been a great general mountaineering and passable ice boot for me. Good durability in my case and I'd buy them again.