We currently use web.py + gevent to run our API where I work. It's really easy to work with since it's so tiny and simple, and since we only need JSON in and out for now, it's perfectly sufficient.
Before web.py, we were on a scary Tornado implementation. The API was rewritten to web.py in a week with a minimal delta. We won't be on web.py forever, and gevent sometimes kicks up minor fusses, but I think web.py has given us a nice malleable form that helped us get out of a terrible place, and we can easily hop off once we decide where we want to be.
I'm not very familiar with Tornado (we've switched to mostly Flask now) but I'd be interested to know what kinds of problems cropped up that lead you to switch to web.py
Before web.py, we were on a scary Tornado implementation. The API was rewritten to web.py in a week with a minimal delta. We won't be on web.py forever, and gevent sometimes kicks up minor fusses, but I think web.py has given us a nice malleable form that helped us get out of a terrible place, and we can easily hop off once we decide where we want to be.
RIP aaronsw.