The great thing about Proboards is that they offer great support. They have a dedicated forums where you can get feedback on your own proboard forum, coding, graphic design requests etc. I found this to be an exceptional service mostly when my forums server had gone down. I received help in an hour or so.
If you are willing to invest a bit of money I would then say vbulletin I suppose as you can do a lot of editing with them but you need the expertise to really make any dramatic changes.
Small Event Management Business Owner