I have a decently sized vBulletin based community that is almost 10 years old. I started it on vBulletin 2.x and upgraded it through the years. I was always an early adopter to new versions, because back in the 3.x days it was worthwhile. I remember Kier posting bits about the new vBulletin 4, so when it was finally released, I jumped right on it. I spent the money with a developer to do a really nice skin (at the time no one had even skinned one). Looking back now, I would have never upgraded as it seems the site has suffered greatly from it.
For the past 6 months, my partner and I have been working non-stop on the site to combat the traffic decline. I'm 100% positive that the SEO related changes that have been made will prove positive in time, most of it is common sense stuff. We have actually noticed ranking higher for certain things.
I've notice the traffic falling off, but did not know why. I ran across this thread - https://www.vbulletin.com/forum/showthread.php/344036-Very-HIGH-Bounce-Rate-since-VB4-upgrade and decided to further investigate when I made the vB 4 switch (prior to today, I couldn't remember).
I found that I made the switch in May of 2010. I analyzed traffic for a 30 day period immediately before the upgrade, and 30 days immediately after (there is a blank period in analytics where my code was not on the page).
Traffic is as follows:
Before vB4 / After vB4
Bounce Rate: 35% / 45%
Pages|Visit: 7.3 / 5.4
Pageviews: 1.2M / 900k
Unique Visitors was not hugely impacted. It was around 55K per month before the upgrade and right after. Its been on the increase and last month was at 90k.
So with the exception of Unique Users, every statistic I have in Google Analytics has been on the decline.
The last 30 days shows the following...
Bounce Rate: 55%
I am really interested in seeing what a move to Xenforo will do for the community.