Is Google App Engine right for me?
I wouldn't worry about any of this.  After having played with Google App Engine for a while now, I've found that it scales quite well for large data sets.  If your data elements are large (i.e. photos), then you'll need to integrate with another service to handle them, but that's probably going to be true no matter what with data of that size.  Also, I've found BigTable relatively easy to work with having come from a background entirely in relational databases.  Finally, Django is a somewhat hidden, but awesome, "feature" of Google App Engine.  If you've never used it, it's a really nice, elegant web framework that makes a lot of common tasks trivial (forms come to mind here).
I am thinking about using Google App Engine.It is going to be a huge website. In that case, what is your piece of advice using Google App Engine. I heard GAE has restrictions like we cannot store images or files more than 1MB limit(they are going to change this from what I read in the GAE roadmap),query is limited to 1000 results, and I am also going to se web2py with GAE. So I would like to know your comments. 
Thanks