Have you considered rollers? Something like this: http://www.sportcrafters.com/welcometop.htm. They do not offer the same resistance as trainers (though still plenty for most people), but are better for working on form and are no risk to your bike. I'm sure technology has come a long way since I last used a resistance trainer (20+ years), but I've always found them to be too loud. Plus, if I'm going to be riding indoors, I like the feel of "riding" my bike, versus just sitting on a bike spinning my legs.

An old thread, for further consideration: http://www.bikeforums.net/showthread...er-vs-Trainers

Also, keep in mind that, because you are not out in the open air, you tend to sweat more (or maybe it just doesn't evaporate as quickly?). As a result, you can drop a lot of corrosive sweat onto the bike. This is perhaps more of a threat to your bike than the rollers/trainer itself.