I like Strava.
Mainly because it's a fast and convenient way to track my miles/speeds. Punch button on Android "on", punch "off" when done. Then off to the shower and to get a snack. A bit quicker than a spreadsheet cross-referenced with the cyclo-computer, and it has a neat little map and an approximation of calorie burn.
Aside from that, I don't really care about the other bells/whistles/"prizes"/etc.