In avast 4.8, essentially no, most of the differences are of a non-security level, like no automated actions, scheduled scanning, the user requires interactive input upon detection, a less configurable Interface.
This however is about to change when avast version 5.0 is released and some functionality won't be in the free version. This however, won't leave the user any less well protected than they are now and some other aspects will be available, the same single user interface, automated actions, scheduled scanning, etc. will all be available as will a behaviour shield.
There isn't a definitive comparison for avast 5.0 as far as I'm aware but you have probably visited this page - avast! Home V Avast Pro differences
http://www.avast.com/eng/av4_version_comp.html. So I would imagine that there will soon be a comparitive page for avast 5.0.
