It seems that I don't get a whole ton of spam, and get less when I bother to use the obfuscation. That said, anti-spam measures are pretty robust at any of the main webmail services (google, yahoo, even whatever hotmail got renamed to), so it could just be a side effect of that.

Realistically, I like the approach the Enigmail team wrote (they were talking about publishing your GPG key, but it applies):

"There is nothing you can do to prevent spam from littering your inbox. Trying to stop it is like King Canute marching into the sea, commanding the rising tide to turn back. It didn't work for King Canute and it won't work for you.

There are excellent ways to stop spam. Blacklists, whitelists, Bayesian filtering, ISP-level solutions and more. Some of those options work better than others. All of them work better than the naive "if I don't publish my key on the keyservers, then I won't get spammed" strategy. "