If you think gmail has a high rate of false positives, I encourage you to try Hotmail or (especially) Yahoo.
For example, I get a few very similar Canadian pharmacy junk messages every single day. Even though I usually mark them as spam, they continue to appear in my inbox. It never learns. Additionally about 1 in 4 order confirmation emails ends up in the Junk folder.
My understanding of Bayesian spam filtering is that it's supposed to get better over time, not worse.
(i use gmail primarily, but have an old Yahoo! address for bacn)