speed of spambayes?

[Paul Rubin]

Can someone using spambayes tell me about how fast it runs?  I'm using
Spamassassin right now but it takes around 1.5 seconds to process a
message on a 2 ghz Athlon.  I believe part of that time is spent doing
network lookups to check the source addresses against various spam
blacklists.  I want to crunch through several gigabytes of spam
folders to see if any legitimate messages got trapped, so need a fast
classifier with a low false negative rate (it's ok if the false
positive rate isn't so low, since almost all the messages in these
folders are already spam).

Thanks.