I have a trainer. It's boring, but it's got such a low "excuse level" that I end up using it. By excuse level I mean the number of possible excuses that might prevent me from doing it... for example "it's cold outside", "I don't have time to go to the gym", "I forgot to pack my workout clothes", etc. Having "it's boring" be the only possible excuse is hard to beat.

That being said, I like running, and I am able to run in colder weather than I would bike in. I also like cross-country skiing a lot, though that takes more time and planning (usually can't do it in the city).