I used one on wet days last winter but I remember it seemed to do me absolutely no good. I've also read here about people cycling miles and miles on the things and then when they get out on the road they can barely do a couple of miles.
Last week I started using a different exercise bike on a few wet days. I just did 10 miles, about four nights during the week. Using my HRM everything seemed to be right and I'd got a good sweat going by the end of it. I went for a longer ride than I've ever done yesterday and I felt well able for it. I can't help feeling that those few miles on the bike each night kept legs in working order.
It reminds me of what I heard that during the Tour de France the riders would do training rides on the days off to stay conditioned. That struck me as counter-intuitive for a "day off", but I guess it works for them.
I've had a LifeCycle for years. It does give you a workout, although you are only in a semblence of a usual riding position. The problem is that it is totally boring to me. Tonight, I went to two places selling exercise gear. I tried the recumberants and ironically only liked one of the cheapest ones in the stores. The eliptical machines I really enjoyed. Truly thinking of getting one, but they won't simulate riding by any stretch of the imagination.
I'd try out some of the exercycles and see if you'd be using it enough to make it worth the purchase. I'd make sure that it could be programmed to simulate different riding conditions. I'll say from my experiences tonight that the heart monitors I tried out were very inconsistent, so, if that's important, test it out. For me, personally, if I got one, I'd also want to check into its durability. Two of the machines I tested tonight were already malfunctioning. On the other hand, my Lifecycle is still going strong after over a decades use. It's been ridden a million times and still functions...although in a boring sense, at least to me. I can ride for hours on my regular bike and feel alive and involved, but the 24 minute cycle on the lifecycle seems to last an eternity.
IMO exercise bikes are better than nothing, and can help you maintain some measure of fitness through times when you can't cycle outside ... but a trainer would probably be a better choice.
When I first started cycling, I took the winters off entirely ... each spring was like starting all over again. Then I started using exercise bikes in the winter and that seemed to help some, at least I wasn't starting completely from scratch. Then I switched to a trainer, and that is even better - I'm working the same muscles as I would when I'm cycling outside, but I still find the trainer easier than riding outside. Now I ride outside as much as I can all year round, and suppliment that riding with the trainer.
I recommend the LifeFitness 9500HR. I train on this bike during bad weather (and actually work for a company that manufactures and interactive bike system that uses this stationary bike as a platform). We chose it because it is the most popular model (at least in North America), is durable and fairly smooth to ride > if you get the belt driven model. Not sure of its availability overseas. Lots of companies sell them used. If you are serious about a stationary bike, whatever you buy, I highly recommend the commercial model.