I've had a crux lite for about 5 years now. It works well as others have stated. Boil times decline quickly with wind, but otherwise it boils fast. I use an olicamp pot with the heat element on the bottom and it speeds up boil times significantly. It's been awhile since I did the testing so I don't remember the times but it boiled 16 oz. of water (inside, so wind free) in about half the time of my Primus ETA Lite, which surprised me. With the Optimus pot that came with the stove the boil times were closer to the Primus stove. Add in some wind and I'm sure the Primus stove would start to boil faster than the Crux but I haven't tested them in the wind side by side so it's just anecdotal observations on my part there. I also have a cheap Etekcity stove from amazon that is very functional for the price but it had slower boil times and isn't nearly as well built as the Optimus.
I've used the Crux Lite above 10K elevation on numerous occasions without issue. The only time I had a tough time boiling water was at about 8,500 ft. but the temperature was about 15 degrees and I had a smaller 4 oz. canister that I let get cold. I now use a full 8 oz. canister and do my best to keep it warm when I know I'll be below freezing temps and haven't had an issue since.