I voted "no" to both 3e and 4e, but its not entirely accurate...
I have used some very limited 3pp stuff. Mostly, either Necromancer, Gamemastery, and DCC modules (and any associated material from it, such as new spells or items). Also, I did allow a PrC found on a fansite for my artificer (since non-Cannith WotC artificer PCs are nonexistent). Oh, and I used Monte's ranger until 3.5 came out.
BUT
I haven't used 3pp monsters, spell, magic items, classes, race, prestige classes, feats, etc. For the most part, WotC satisfied my need for these things and I never found need to look at unofficial sources for them.
This may change with Pathfinder, but right now I've been happy with my 99.9% WotC games.