General google app engine questions

All, I started researching cloud hosting today and I have a开发者_运维技巧 few questions for the google app engine experts among us. Thanks in advance. I have a cloud service I'll be offering and, very simplified, it consists of a pretty basic web UI where users upload / maintain several files to the service, some fairly intense db processing then occurs, then some new files are transferred back to the client. It's currently in MS .net, absolutely has no reason to be, it's pretty straightforward code and sql and could be done in most any language. So I'm really flexible as to what platform I go with. Originally I was thinking php / mysql would work great, but it seems these pay-for-what-you-use services like google app engine are much more cost effective than dedicated server hosting. That's also another feature of this service, it sits idle probably 99% of the day, but when it gets hit, it spikes the server for a few minutes during processing, then essentially goes back to sleep. I have more experience in java / C# than anything else, so I started looking at google app engine today, thinking java would be the way to go. I'm not averse to learning python, it looks pretty straightforward as well, so on to my questions:

1) I worked through some GAE tutorials (java ones) and it looks like jsp is the web technology they use. I've done some jsp in the past, and I was comfortable with it, then I realized the last time I used jsp was about 10 years ago and I sure don't see much .jsp these days. I guess in the last few years, php has kind of taken over the web and I'm hesitant to commit to jsp if it's on it's way out or has negatives. I'm curious what everyone's thoughts on this are.

2) If I went the python route, is there a corresponding web tech for python, like a php / jsp / asp?

3) I don't necessarily need a relational db, but it would be a plus as I'm super comfortable with sql. Is big table a decent alternative?

4) Considering the architecture, files being uploaded and sent back to the client, any gotchas with GAE that jump out to anyone?

Again, I appreciate the advice, and I'm trying to figure out the best way to go here, the budget for this is not huge at all.

I was knee-deep in GAE for more than a year. Briefly:

1. Haven't touched Java on GAE, and haven't written JSP in more than a decade. I mostly do consumer web stuff, I'm sure the enterprise guys have a different story
2. Yes, it's called Django
3. Totally depends on your schema, access patterns, and use cases. There are scenarios where Google's implementation of BigTable shines, there are scenarios where it is a nightmare.
4. You are limited on the max file size you can upload; you have have to use their BlobStore or Google Storage for Developers, or S3.