I have spent the day looking into parse.com and here is my current opinion based on what I've found (Please bear in mind that I have only very brief experience of developing with the SDK as yet)..
Parse.com clearly has some very attractive positives which is why I found myself looking into it, but for the sake of debate I will concentrate on being critical as the great positives are all listed on their website. (Well done parse.com for attempting to solve such a great problem!)...
- In the testimonials, Hipmunk is the biggest name I would say. It is listed as an app which uses the data portion of the SDK. Without approaching Hipmunk developers, I can't know for sure but I can't imagine them storing ALL their data in the parse.com cloud.
- After trying and browsing most of the apps listed. None really stand out as being hugely dependent on a server back-end so I find it impossible to get an idea of whether or not scalability has been solved using parse.com based on these.
- The website states 40,000 apps and counting. I feel (but do not know) that based on the app gallery, this figure is based on the amount of apps in their user-base, and not real live production apps in the app-stores. The app gallery would feature far more big names if that many apps were using parse.com.
Parse.com is a very new concept, and very different even to its closest rivals. So without concrete evidence on how scalable and stable (and all the rest) it is, then it is very hard for a developer on a project to consider committing to it as there is too much at stake.