I use 4 as my cut-off.

Here's mine:

rewrite_subject 0
detailed_phrase_score 1
required_hits 4
report_header 0
use_terse_report 1
fold_headers 0
spam_level_stars 1
defang_mime 1
report_safe 1
use_bayes 1
bayes_auto_learn 1


(I don't like subject-rewriting, as I have mailfilter rulesets in place that divert spam to Junk folders)