Mountain Biking - How good is my Cannondale F400?

Hi. I'm a new member to the forum, but have been reading posts for the last few weeks. I am just getting back into bikes after a long period with a cheapie Mongoose that I used in college to ride from class to class. I bought a new '05 Cannondale F400 about three weeks ago and have loved every minute of riding on it. I wanted to ask if this bike is built well enough to actually use on trails. It seems like it to me, but you guys are much more experienced and I thought I'd ask your opinion. Can anyone let me know of their opinion on this bike and and of any advisable upgrades? It's got the headshok which seems pretty cool so far -- when I'm climbing, it's nice to lock it out so I'm not bouncing up and down wasting energy. I live in Chicago and it's pretty flat here and there aren't that many trails around, but I'd like to take it off-road. Thanks for your advice, guys.

that bike was made to be ridden off road, it is a mountain bike after all.
It may seem light, but that is fine, it is meant to be ridden as a "Cross Country" bike so obviously it won't handle big drops, or gnarly downhill too well, but as far as just taking it out on a trail, yeah no problem there, it will be just fine.

Actually one of my riding friends have one in grey and it's a really nice bike. I even like the single Shock for the 2 forks. The adjustment is neat. The bike is really light.

For trail riding , 27 speed allday long man.

The F400 is an incredible bike for the money... the frame is their "Dual Assault" geometry which is extremely stiff and designed for aggressive riding. One of my friends rides urban with us on his wife's F400 because of the geometry... short stays, higher head tube, and beefy construction. Excellent frame and bike overall. The Headshok is also a great design, extremely stiff + simple to service for any Cannondale shop. Don't be afraid to ride the bike hard, but do remind yourself its a cross-country bike, not a bike to be hucking off a 6' loading dock.

Hi. I'm a new member to the forum, but have been reading posts for the last few weeks. I am just getting back into bikes after a long period with a cheapie Mongoose that I used in college to ride from class to class. I bought a new '05 Cannondale F400 about three weeks ago and have loved every minute of riding on it. I wanted to ask if this bike is built well enough to actually use on trails. It seems like it to me, but you guys are much more experienced and I thought I'd ask your opinion. Can anyone let me know of their opinion on this bike and and of any advisable upgrades? It's got the headshok which seems pretty cool so far -- when I'm climbing, it's nice to lock it out so I'm not bouncing up and down wasting energy. I live in Chicago and it's pretty flat here and there aren't that many trails around, but I'd like to take it off-road. Thanks for your advice, guys.

Your bike would definitely be fine on trails.
As far as upgrades...you have a lot of Cannondale components on your bike. My experience has been that Cannondale makes great frames and offers some decent components, but lowers the cost of their bikes by putting their own manufactured parts on it. Upgrading any of these would be advisable. You've got Cannondale hubs, handlebar, brakeset, brake levers and saddle that came on your bike. I ride an F600 and the first thing I changed out were the extremely cheap brake levers...pedals are next to go.
Have fun on the trails!

Thanks for all the replies, guys. I'm relieved to know that what I bought can actually do what I want it to. I was up on Mackinac Island, MI last weekend and there were a ton of trails I wanted to check out. Unfortunately, my girlfriend prefers to stick to paved surfaces and I couldn't go off and disappear for hours to explore. I'll have to look into replacing the breaks and levers. I've also been thinking about going clipless but haven't decided yet. I do ride an awful lot in the city to run errands and for excercise and don't want to always have to wear the shoes so maybe a clipless with platforms? I'm still new to off-road biking in general but I am hoping to get into it a lot more.