Google App Engine Pros & Cons

Here is my findings about Google App Engine after I have spent 4 months to develop my Social App Happy Friday.

Pros:
1. It is FREE (until your app has tons of user)
2. It supports Java & JPA.
3. It supports scheduled task.
4. It has free Mail services so that you can notify your users.
5. It supports URL fetch.
6. It can be integrated with Facebook. (I've tried this before)
7. It supports Struts2. (I've tried this before)

Cons:
1. Its db is not relational, you have to learn some new idea such as BigTable, Google File System, Entity.
2. It does not support JOIN SQL.
3. It does not support predicate conditions on 2 different properties such as (..WHERE a > 10 and b < 10)
4. It does not support transaction across 2 different entities not in the same entity group.
5. It does not provide Java tool for data export and import.
6. It does not support function such as MAX, MIN, SUM, COUNT...
6. If you add primitive property to the entity, you cannot retrieve the old data, you have to delete it and add it again. There is no SQL for you to create or modify the entity.
7. It is not easy to implement Full Text Search on GAE.