To compare, my first vBulletin forum has been up for four years and has about 10,000 threads and over 150,000 posts. In total, Google has indexed 4,500 pages.
My vBSEO forum has 5,000 threads and only 12,000 posts. With vBSEO, Google has already indexed 7,000 pages. That number continues to increases every time I check.
From Google Analytics, over half of my traffic comes from search engines. That was a big shift considering before SEO, my site was all direct traffic & referral.
For search query, moved to 4th on Google, first on Live, sixth on Yahoo, fifth on altavista.
Member wise? Still slow. I've added another 100 members and done the best I can to keep them active. Still early to tell, but Adsense revenues have gone up as well. So far, I think it is a worthy investment, just need patience.