1) Unless you're building a mobile client for an existing website, would you really bother with authentication? Can't you just transparently store users with a UDID?
2) Client-side caching is the biggest pain in IOS apps. Network calls are relatively easy. I try to make simple/dumb calls to the backend and just do smart filtering and data manipulation on the front end. Parse doesn't really help here. Do they have integration with core data? They don't even seem to mention it.
3) Some of those testimonials are hilarious, but clearly fake. Why not use real ones?
4) You usually need a server running for a landing page, anyway.
5) No support for storing images or audio. Storing simple strings isn't that useful.
Anyway, just my honest feedback :) Good luck!