I got a Diamondback DBR series bike ( dual suspension ) back in the late 90's to work on fitness, and off-road is definitely more fun ( and harder on you ) than roadbiking imo. Rigid bikes are easier to ride on-road vs. full suspension bikes on-road since they soak up so much of your power when pedaling hard surfaces. But taking a rigid off-road will surely kill your joints, ass, back, and balls vs full suspension. Mine was about $1600 new - 27sp, dual hydraulic disc, RockShox susp fore and aft, "good" Shimano hardware, and ball bearing EVERYTHING ( even the pedal stems ) so once it's cruising it doesn't want to stop. Quality can't really be found in your local dept. stores so if you want one that will last, stop into a dealer for serious rides. On-roading is tougher on a full susp bike though, so for fitness it's almost a win/win no matter which route you want except for the tire wear. My knobby's are rolled pretty bad from high gear runs on country backroads, but I LOVE the fact that I can hit the streets to the trails and then have a bike that can tolerate off-roading extremes