I'm not so fond of my trainer. I find I rock back and forth on it and it really bugs me. But I use it on days like today when it's ten degrees with 40 mph winds and a run just doesn't seem possible.

I do my intervals this way: I turn on my mvp player to random and during fast songs, I up the cadence and spin to the music for the full three minutes of the song. If that is followed by another fast song, I'll unclip one foot and do the best I can to pedal rounds on both sides to the end of that song. Slow songs I have to go into the big ring and get out of the saddle for the full three minutes, even if it is at a resting pace. I do this for eight songs, and then a half hour has gone by and I get off and go do weights.