I am hoping next spring, I will be ready to go! I have had a Treadmill and Recumbent bike for years, and I use them religiously in the winter, but come Spring, while I may be in good shape, I am not in good 'Biking' shape, and it takes me weeks to get conditioned again. I started using it in August, and I can tell you now it has increased my performance. It doesn't get boring for me, and the time flies by.
I purchased a series of Spinner workouts at Spinervals. Other than that, it's like riding outside, except there is no coasting. I say almost because I have the seat tilted just slightly back, because without the wind, I seem to slide forward. I purchased a Commercial grade Spin bike for my basement Gym, and it is set up almost EXACTLY like my road bike. But if I had no other option, I might consider it. For me, if I had to go somewhere to do the Spinning, I wouldn't do it.