1> Do the kind people here on this list recommend using new rulesets that are not part of the core spamassassin distribution, and;
I'm hardly a neutral unbiased opinion, however I do think using add-on rulesets is a good idea, if done with proper care.
These are a few cautionary points I'd suggest considering:
1) watch your RAM usage. Some of the add on sets are rather large and chew up a LOT of memory. (bigevil and sa-blacklist are notable examples).
2) I'd suggest adding a small number of rulesets at a time, monitor their results, then add more if you feel the need.
3) be aware that some of the rules have some potential FPs.. Check the mass-check listings, and keep an eye on your own results.
4) I'd suggest choosing rulesets that are designed to address specific problems you have, as opposed to just grabbing a handful of rulesets "just in case".
