UPDATE: The vBulletin update was completed on 4/17/2012 -- post feedback/questions in this thread.
Just an update. Some of you may have had problems connecting about 10 minutes ago. The support group was installing some monitoring software and needed to do a quick reboot. Most of the performance tweaking has now been done, although I will be monitoring things and could possibly add some more RAM to the server, but right now it seems to have plenty.
cbiweb who migrated BF to vBulletin version four last month is working on the upgrade to the latest version of vBulletin. He's testing this on our vBulletin test site. This is a minor upgrade compared to last time, so "in theory" there should be no impact to users, other than about 60-90 minutes where the forum will be turned off during the actual upgrade. This will be done either late tonight or late Monday night.
There are a number of bug fixes, that make this upgrade worth going to. In addition, after the upgrade, you will have another mobile access option, http://www.forumrunner.net/
Forum Runner is a paid app for Android and Iphone ($1.99 I believe for full version, free for read only version), and they claim to be working on Blackberry and Windows Phone versions. The money goes to Forum Runner, not BF. While I haven't used Forum Runner yet, it is supposed to be a very good, mature mobile app. So, once it's an option, you can download the free version if you want, and if it's a better way to access BF from your phone/Ipad, then you can decide if you want to spend the $1.99