I upload to strava so it will work out my time up certain hills for me. Also so that I can see my power and time on a time trial or hill climb course and compare to other peoples power (I am talking about looking at the real measured power values here, i.e. ones with the little lightning strike next to them, not the made up values).
It is marginally useful (and the social side of it can be quite fun now and then), I don't utilise much of it tbh, and I would NOT pay for the PREMIUM analysis features (which are basic and can be had for free elsewhere). It would be great if Raceshape (which utilises Strava) implemented a feature to let you compare between several of your own performances rather than just allowing comparison of your best run vs someone elses best run, that would allow for various pacing strategies to be compared.
AFAIK, my recently uploaded rides to Strava will not be entered into league tables etc as I keep my activities private except for races, for various reasons.
For my serious analysis I use Golden Cheetah on my desktop, it is free and has very good analysis tools. I use Training Peaks online as my coach inputs my plan, then I just upload my file for each planned session once completed (and also any comments), he can then look at the data and comments from his end and reply or make his own comments and changes to my plan etc.