for hobbyist use.. I like it.. mostly..
Funnily enough I've just started developing an app using app engine.
I do a bit of python coding at work, and have worked on simple small company intranets in pylons, but to be fair it was a fair few months ago and I spend most of my time developing in excel
I came up with an idea for a simple web application that I'd find useful (and probably a fair few other people) a while ago and wondered about coding it up myself in my spare time, it'll add a little to my CV at least and be useful and interesting too.
Then I wondered about hosting... Any webhost that would let me setup server side code generally seemed to require a $$ a month commitment, which considering I was doing this as a project for my own amusement in my spare time, I wasn't too keen on... especially as I wasn't sure if it would all work in the first place anyway.
Then I heard about app engine.. free, runs python..
So far I've only developed locally on the dev server, I haven't uploaded yet.. Thoughts..
They say you can run whatever framework you like on there (Django, pylons cherrypy etc) but it seems far from trivial to get it setup, plus certain restrictions in gae break features of the framework. So I've stuck to the simple framework they have. My app isn't too complex for the most part so it's fine..
But.. some of the restrictions and so on do take a bit of getting your head round... there's no session management to speak of builtin so you have to rethink the way you might normally do things to get it to work.. It's easy if you expect users to login to their google accounts.. but if your app doesn't use google services then that's not massively helpful..
Documentation and tutorials are pretty good..
Of course I don't know how well this would suit a proper business.. Also not sure what I will do if I start to hit the free limits in terms of bandwidtth / cpu and google require cash of me to pay for it... I guess this is the point, they will help me setup adsense on there or something to fund the cost..
Basically they got me with the free model.. I have a server setup, that will run the code I want sat there waiting for me, for free.. Of course if what I do is succesful then google may well end up getting me to upgrade to the paid version...