Well, I don't think DEP is
that big feature... if you know it's there, you can probably bypass it as well (if there's a bug in the code), it's just a bit more complicated

Besides, a number of security bugs has already been found in SP2.
In any case, it's certainly better to exclude only some apps from the protection than to disable it completely. Honestly, I don't think there's a big probability of avast! being a target of an attack DEP may prevent.
Anyway, we'll try to release the update as soon as possible - but the update isn't just SP2 compatibility, but a number of other features - and we have to make sure they're OK.