I've visited this subject before, but it's worth repeating. In my experience, the most useless feature in any public bug-tracking system is the ability to vote on bugs.

As I mentioned in the linked article, users of bug databases aren't really representative of the user population at large, and the bugs that get large numbers of votes tend to be the "vocal niche-market" issues that stay unfixed for a long time because they're just not a priority for the people writing the software.

For commercial products, or Open Source products with corporate backing, the features that the paid developers work on will be dictated by the people doing the paying. While votes in the bug database might be some factor in their decisions, it's likely to be a very, very minor one. You're much better off making your requests through the sales channel: ask them what the best way is to get your bug fixed or feature in.

Volunteers for Open Source projects will work first on problems that effect them directly, and then on problems that don't necessarily effect them, but that their pride won't let them leave unfixed. Votes are unlikely to change this schedule. Calls from users to have a bug fixed that none of the developers think is important will be met with replies of "if you think it's that important, we'll be happy to accept a patch".