I have the Cycleops fluid trainer. I rode it side by side with their magnetic trainer, and the fluid was quieter and felt more like riding on the road. Both, however, are incredibly boring IMO. I'm with Tulip on this one. I'd rather do just about anything else during the winter. I may resort to it this year, but not without some complaint.

If you do it inside, get a fan, too. I get overheated when I use it indoors. I prefer to set it up in my garage.