Hats off.
Parse is the first of all these backend-as-a-service startups to face and solve the biggest problem in the web context: user authentication and data security.
By offering a full signup service with email verification and user-level control over the database they have eliminated perhaps the most redundant piece of work that just about every web app has had to implement.
Lock-in is of course a concern, but that hasn't prevent some AWS services from taking off big time. Perhaps in the near future one will see an open source project that offers an off-the-shelf backend with a Parse-compatible API, much like what happened to S3 and etc.
Pricing on the other hand is a concern, particularly if your service requires background workers that constantly update the database -- every update is an API request hit, and one can only wonder what they charge beyond their Pro account.
Overall, I think this is a huge step in the right direction. Because it's the 21st century and one shouldn't have to reinvent the wheel every time one writes a new web app.