Many people don't like training on indoor cycles or trainers. K thinks it sucks. I like it. The suffering inside (not necessarily from exertion) really makes you appreciate riding outside just that much more. Besides the obvious advantages of being able to lock in to the HR you want, you can control your terrain and weather, you also don't have to hassle with helmets, glasses, a flat kit, and the other necessities you need for an outdoor ride. Also, some high ranking coaches believe that for every hour indoor, you should credit yourself with 1.25 hours of ride time. I believe they say its mainly because there is never any coasting for corners, downhills, etc--you're always pedaling.
Anyway, I put in my longest ride of the year so far--2.5 hours. I actually attended a cycling class for a change. Joe M. was there as well. When he was done he logged over 3.5 hours on the bike then he hit the treadmill...(freak!).