I am trying to learn python by created
some simple web applications on Google
App Engine using Eclipse + Pydev for
development.
This seems reasonable. Nothing wrong with using GAE, Eclipse, and Pydev to learn to do Python web dev.
So far I have some basic functionality
working in App Engine, though I have
had some frustration with some library
imports not working and whatnot (this
may not be app engine specific).
So, is it worth it to switch now to
webfaction, and leave GAE?
You haven't provided much of a reason to leave GAE now that you've started there. I think that "some frustration" is normal for learning on any platform.
Beyond that I think this could descend into a general GAE good for learning vs. GAE bad for learning discussion.
So let me get that started...
Since GAE is a 'Platform as a service' (PaaS) it makes deployment and maintenance very simple. You can get right to coding and not worry about the platform. As well, this platform provides some services, such as e-mail and authentication that make those tasks very easy. For example, on first pass you can just make use of their authentication API (supports Google and now openID authentication I think) and leave more complicated authentication options for later.
On the other hand, this platform is kinda' non-standard. The datastore is the main issue and that affects Django. That's a pain because it means that the Django running on GAE is slightly different then the standard Django and the Django docs that you are reading might not apply for GAE, etc.
Here is a current thread about getting started with Django on GAE (which addresses the datastore issue):
http://groups.google.com/group/google-appengine-python/browse_thread/thread/8d1c945d27b6305f
Hope that helps.