I have a 2005 Rocky Mountain Vertex Team race (hardtail). Love this bike, and I would consider myself much more of a XC rider than anything else. This bike doesn't weigh much more than 20 lbs and it just an incredible overall bike.
I also own a 2006 Giant AC2. While not a complete downhill bike, it sure as hell isn't a full suspension XC bike. Pain in the assay and way too heavy to pedal up hills for any amount of distance
I have been to Rabbit hill a few times this year and really get a kick out of it. But have not had much time due to work to travel too far for weekends just to bike.
I really enjoy both, but if I had to choose between a day of downhill and a day of XC riding in equally beautiful (respectively) conditions and locations I would probably choose the XC ride.
*EDIT* - Last year I put road slicks on my Vertex because I was going to consider riding to work at least once a week during summer.
My ride is basically 50th St/167th Ave just off manning freeway out to the Shell Scotford site. This is a 76Km round trip as driven by car. Physically I had no problems doing it, however riding a bike on the highways out to site are simply INSANE. You are just rolling the dice and gambling your life being in anything other than an enclosed vehicle on these roads. I couldn't count the number of times I was nearly hit, or blown off the road by giant truckers. And this was during broad daylight.
I will never do that again, and will just settle for biking around after work and on weekends.... There are other ways to get exersize that don't involve me having a one in six chance of dying everytime I go out.