I may not be the best to comment, considering that before my RM I hadn't purchased a new mountain bike since the early 90's.
I can say this: technology, frame geometry and equipment are vastly superior when compared with my last mountain bike!
I find the frame to be very stiff and snappy. The finish is a nice flat black (matte) and the welds look solid. I've put about 500 miles on my bicycle since I purchased it in the fall and I've had no problems. I'm riding some fairly rooty, rocky terrain and I don't leave much on the mountain when I ride. It climbs easily and the wide flat bars contribute to its quick responsiveness.
How did I choose RM? Well, I was looking for a quality entry-level build that would be worth upgrading if I desired. I thought about single speed and was considering a niner or surly, but as a did more research I decided I wanted a geared up ride. I looked closely at Kona, Specialized, and even the Performance Bikes line. I started looking at RM because their frames are handmade here in North America and I heard some buzz about their foray into 29er geometry. I was really attracted to the North American product and ended up purchasing the vertex after I saw good deal on a 2010 model. I bought it before I had a chance to ride it... but I was given a 30-day trial period to return it. After my first 5 miles of single-track I knew I'd be keeping it. It just feels good to me.
I'm 6'2", 195 pounds and I bought the 20.5" frame.