If you suffer from arthritis or other joint problems that hinder your pleasure outdoors in cold, wet weather then a turbo is brilliant.
Variable resistance is useful but I tend to not vary it during a session (or to vary it to break up a long session into smaller periods, like 1 hour + broken into segments of 20-30mins) even if I am using the ss. A computer on the rear wheel is handy (I have the computer on the rear wheel on all my bikes where I can, wired with the captor on the seat stay and the monitor on the top tube, just behind the head tube; you might need a high-power magnet on the wheel, I do).
For longer sessions something to watch, tele or video, helps to combat boredom; audio is ok but video is better. Having a session plan with changes of cadence, gear, intervals, sprints etc also combats boredom, even if it is not a tailored training plan.
I bought my turbo from a neighbour for 40€, an old Tacx Cycletrack and I think it is wonderful for keeping my arthritic knee flexible in the winter. I would use it even more if I could keep it set up permanently, instead of having to put it away every time. However it is not a very effective way of losing weight!