Our host is getting whiny about server processes - I've switched a personal site over to 1.5 and really like it, but here we don't really need to fix something that isn't broken. If 1.5 uses less server resources we'll do a switch, if increased functionality would create more overhead it wouldn't be worth it. If it actually decreases that'd be wonderful.
Ran some searches in the forum and hopped in IRC - no help there as no one intimate with the source code was on so I mailed photomatt directly (though he said he doesn't reply to WP support stuff this isn't a basic config question the average person can help out with). I'm posting here to cover all bases.
update - only running the Show Category Posts (1.4) and Search Hilite plugins