Hi, I rode moutain bikes for years when I lived in NY but moved to the midwest and traded it for a cross bike. It's a great bike but I mainly ride it to work. I know people ride off trail and found some good trails not far from my house. Without suspension, how heavy a trail can I ride? Fire trail seems doable are people doing singletrack, technical riding,etc? Let me know, I have a Bonfire Empella, seems far more sturdy than what I am using it for.
I raced my CX (Scandium Salsa w/ Ritchey Pro fork) bike the other night on a short track MTB race and it was pretty rough/rocky in spots and I beat the hell out of my bike. I was watching the lines that the MTBers were taking...they didn't really have to think about a line, just go and let the suspension do the work. And then there was the "cyclocross line" that I was taught to appreciate a long time ago, adds a lot more dimension and fun to your riding and skills. I got 12th out of 35 racers. Guys could kill me on the descents but it became a game of cat and mouse on the climb being that the cx bike is lighter. If I didn't have a family to raise and more huevos I could see being faster...maybe after several more races. I think that CX bikes can take a beating but you have to ride with agility and finesse.
a year ago I did a two-man relay in an eight-hour mountain bike race. i took my cx bike and my mtb (29er hardtail with susp fork), and alternated bikes on laps.
it was pretty technical singletrack, and rode 700x38c ritchey mount cross tires. when leaving the start/finish on my skinny tires, some guy shouted "I hope you have lots of tubes!" and chuckled. I'm not quite sure why he said that, as he could see I had a downtube, seat tube, top tube, and more. I was all set.
anyway, the lap had a bunch of rocks, roots, and fireroad climbs. and it was hard riding on my cx bike. but to my surprise, i was a few minutes faster on the cx bike than my mtb each time. granted, by the end I was hurting more from the effort (mostly had to do with being over-geared on the climbs). there's no way i could have done 5 laps on my cx bike, but it showed me that for a shorter race, a cx bike can be just as fast if you're comfortable on your cx bike and can get tire pressure right.
Personally, I ride singletrack year round with mine. 35c clinchers at 50lbs/pressure and I weigh just under 200lbs. The singletrack in my area has a large amount of exposed roots combined with mud, but no rocks at all. My ride has no problem with that and I enjoy the heck out of it.