I've been using the Kreitler Poly-lite (3" drum ?) rollers with the squirrel cage fan with my fixie (48x15 gearing). Using the fan at full resistance provides a pretty challenging workout, although it's noisy as hell. You can stand up and sprint, sort of, but it's pretty difficult to maintain balance.

I personally prefer rollers over trainers. There's just something more natural about rollers, since both wheels are spinning, and you need to balance. Unlike trainers, rollers force you to focus your attention on your workout and your pedalling form. I feel that this reduces considerably the monotony of training indoors.