In reply to atlantis:
Oh, I meant to add, it made me laugh when I raced some years back on a regular basis and heard all these other bikers bragging and comparing how much more they spent on their bikes (this was before my first race)..
only to be left behind when I whipped their butts and came in 1st place out of the females (female race though men and women were racing at the same time) I didn't know I had won until prize giving that evening. As I say, it's fitness that counts not the price of a bike, I never did believe in spending 3K on one as some do. That first bike of mine was a GT timberline, about 400 pounds, and some with over 600 pound bikes were bragging to each other before the race on how much theirs cost, I didn't say a word.
Good quality mountain bikes, 'real' mtb bikes include: Trek, Canondale, Giant, Marin, specialized, to name a few.
I always rode hard tails, front fork suspension only. Downhill bikes are heavier and you don't need the rear suspension anyway unless it is pure downhill biking you intend to do. I am a cross country biker fan, and you still get your hills.
I am also a great fan of V brakes, they worked effectively well for me, and very sharp too. I personally hated disk brakes in comparison, and grip shift which easily moves without you wanting it to due to how your hands wrap around the handles with them directly next to it, compared to manually clicking down and up gears with V brakes(finger control is so much nicer and better for overall control of gear changing in my personal opinion). It's personal choice end of the day though.