I like the segments and social aspects of Strava. The Fitness etc aspects are interesting but I don't take them seriously since I go by how I feel, not what an app tells me - but I also don't really understand the Fitness and Freshness aspects, admittedly. For example, my training and recovery number is currently 130 but goes down 3 if I don't ride. If I chased increasing those points I'd burn out wanting to see percentage improvements all the time. It also seems to reward longer rides regardless of how intense shorter rides are - so more about calories and prolonged heart rate figures than what HIIT can do. Anyway, not too fussed, I mainly just like the obvious bits of the app.
All my rides are uploaded via Garmin Connect so my History is not reliant upon Strava and if it went bust tomorrow I'd not be all that bothered. Still, while it is around, the cost is small so I am happy to have it.