Unfortunately I've seen many, many cases where a good reply goes woefully undervoted. Sometimes it comes along a few days late, or is put so deeply nested in the reply hierarchy that many folks don't bother to dig down to it to vote on it. Other times I've seen good answers to posts that no one is interested in since it is out of the mainstream (e.g. getting perl to build on AIX). I've seen other cases where a short low vote answer was better than a lot of other high vote, fully written out but flawed code examples.

In other words, I would take a high vote counts as a general hint that something *may* be interesting in the reply, but I wouldn't put much stock in taking the absense of upvotes as anything meaningful. The only way for a poster to know what replies are "useful" is to examine the content of each one (and generate followups as needed).