Rock & Roll
I have never used a trainer before but I have ridden stationary bikes at the gym before and don't much like the workout. I have a set of rollers I bought in '05 from Performance bike for $99. They are cheap and awesome.
First, you have to keep your core taut to stabilize, stomach, back, hips are worked, just like they would be in normal riding. On the stationary bike I could slouch, use poor posture and still ride. Things I could not do on a bike. Not optimal. Felt like just a leg work out.
Second, I confess I wipeout on my rollers at times but never get hurt. How? I learned a safe way to use my rollers. I put them in the door way between my garage and play room. I have never went off the front or back of my rollers, always the sides. If I go off I easily catch my self by grabbing the door jams. I can even put my rollers close to a wall and favor that side while riding. When in great form I never go off. Don't be intimidated by rollers. If you can ride a bike you can ride rollers(and yes, I have always used clipless pedals too).
I had a funny wipeout one time when I put my rollers in the garage next to the trash cans. I wobbled and tackled a can! No one there to laugh, didn't get hurt, back to the doors till I got my body in sync. And that right there is why I like rollers, they teach you to maintain proper core muscle tone, body position, concentration and balance.
If I ever wanted something different it would be to one day move up to the Kreitler rollers.(I had put them out of my mind till now, thanks alot guys, another thing on the wish list!)
Again, I have never used a trainer but if it is like a stationary bike I wouldn't want it. Some could argue that "just a leg work out" has it's merits but for me I believe it is better for me to ride like I train, train like I ride. Roller can still be had for a little more than $100. Try it, even borrow a set if you can and see if you agree.