Here's my general method for evaluating discussions:
- First, I read the discussion, trying to ignore the various bolded "support"/"oppose" votes and focus on the actual arguments.
- Once I've finished reading the discussion, I make a tentative decision based on my impression of consensus.
- Once I've got that in mind, then I go back and look at the numbers. If they reflect the same impression I've already formed, then my decision's done.
- If the numbers are close, or are weighted in the opposite direction from the impression I'd formed, then I have to re-read the discussion and determine exactly how to weight the arguments versus the numbers. This might involve outright ignoring !votes that contradict establish Wikipedia policy. For a discussion I closed that went against the numbers, see Wikipedia:Files_for_deletion/2009_May_18#Normal_114788_6298_ful.jpg, which resulted in a delete closure, despite the numbers being 6-3 in favor of keeping the image. I've seen even more lopsided decisions made by other administrators and bureaucrats in the past.
- However, in my experience, most discussions close with the numbers, just because that's how WP:CONSENSUS works: one has to be able to convince other people that one's argument is valid. If you can't do so, then maybe it's not such a good argument after all, no matter how convinced you may be yourself.
- In sum, while it would be a lie to say that numbers of !votes are meaningless, they can certainly be ignored with a good enough rationale. However, you do this at your peril: very few closes against the numbers go unprotested.