It works flawlessly! I purchased a MOTU Ultralite MK3 a few weeks ago and had driver issues with USB on my Dell Vostro 400 tower. It sounded fine, when it worked, but as I'm building a new live looping rig to replace my Boss RC-50 loop station stability was number 1 in my book. This thing smokes. Lowest latency I could achieve with the motu was 256 samples, 198 or 196, whatever increment it was, kinda worked at lower cpu usage but was not consistent. I've run a ton of my projects on this thing at 96 samples no problem. 64 works great all the way up to a 65% use in the cpu test section, but I have to turn my guitar way up to play live at 96 and notice that it's coming through, i.e. low enough latency to track and play live. For reference, this is on a several-years-old Dell Vostro 400 tower, E6550 C2D running at 2.33ghz with 1 gig of RAM
Anyway, it's been said over and over again, but you get what you pay for. Thanks Sweetwater for letting me make 3 easy payments without having to use my credit card. It set up in seconds, I can change latencies within a current set with no problems (my MOTU wouldn't have that). Big thumbs up to the guys at RME. Only thing that could make me happier is if this unit came with the Totalmix FX like the UFX and Babyface have...but I'd check my temperature if I ever found myself without at least one gripe. Just wanted to share and recommend a great product.
P.S. I don't work for Sweetwater or RME...though I should probably invest in some stock of each