I spend a lot of time in the review queues and usually find that flagging is appropriate. I wonder sometimes just how opinion-related a question needs to be to be closed - that's about the only area where things get really ambiguous for me. I tend to give those questions the benefit of the doubt, as giving some discussion of options and merits is a useful exercise for future readers, even if there is some subjectivity afoot.
I tend to flag quite a few posts myself for transfer over to Expatriates, but I find they tend to be pretty obvious.