Hello,
I have it running covering 500 mailboxes, performance is really only limited by the specs of the mail gateway server.
You should use 1.4b as 1.38 has a few bugs that were fixed; 1.4b is also easier to configure because the settings are held in a database as opposed to the notes.ini file.
We've had problems with it running on Linux, e.g. random crashes, non-English email - again random crashes - and some emails being scanned by the REGEX functions. Most of these seem to be rare, but it does happen occasionally on some servers. Personally, I haven't had crashes on my company's server since we installed 1.4b, maybe because I test it on our servers before I release it.
Well written? Thanks :)
Rgds,
Tom