There is no proof that VBSEO add-on helps in any way, shape, form or fashion. Reviews point to just the opposite, that the VBSEO does not help your forum. The nofollow is default for a VB forum. If you "really" want to do something to help your SERP rankings, forum names, site description and very important - a site map generator. Forum names should be treated as keywords, they are very important. Without the site map only a fraction of your pages will be indexed. I have seen VB forums with over a million post have only 20,000 pages indexed with google. On the other hand, I use the site map generator by the same people that make VBSEO and I have over 100,000 pages indexed with google. And my site has about 190,000 post. Also, get rid of that "powered by vbulletin" in your forum description. The forum description is one of the most important changes you can make to your site. On the "welcome guest, blah, blah blah" message, edit that and fill it with keyworded paragraphs. You also have an error in your "welcome guest" msg - "[ARG:3 UNDEFINED]" As for my site and my google rankings as proof, Survival forum - #1 at 10:30am central time survivalist forum - #1 at 10:30am central time survivalist discussion board - #1 at 10:32am central time survival gear forum - #4 at 10:34am central time survival gear reviews - #4 at 10:35am central time I have held the #1 spot for "survivalist forum" and "survivalist discussion board" for months. I have been in the top 1- 5 for "survival forum" for several months. Recently I changed the site description to cover more keywords. My ranking in that has been increasing at one spot per day. Last week I was on page 5, this week its page 4 for the new keywords. Site maps, keywords, back links - they ALL play a roll in your ranking.
I've bought vbseo 2 weeks ago. I can say that I've notice a big difference, but I guess it's too soon. Anyway, for now I'm not sorry for buying it. I really like the features, but I still have to do some seo things by my self.. I wish that somehow vbseo would have done everything for me. But, again, I'm not sorry for buying it. Yet...
the most important seo modification you should do in your forum is the proper usage of <h1> and costum keywords and description for every thread and forum.