Brandon,
Great optimization tips! Your concise bulleted list should save new vBulletin owners a ton of research time.
I found your site while searching through Google looking for additional tips on how we could further optimize
ForumGarden.com
What we have found is that the tips you have listed will reduce a server's load by up to 1/2 if you have a busy forum.
Currently, our largest forum serves about 165,000 pages per day. That may not be gargantuan to some, but it can tax any dedicated server if it is not setup properly.
The *one item I did not see - and the one item that can have a huge impact on performance is whether or not you batch your emails.
We ran for years using the "immediate send" setup. One of the best single changes we made was to change it from immediate send to batched - with locking. (The setting we use is 20 emails per batch.)
If you have lots of users, threads, and many active subscriptions, this setting alone can make or break your load values.
Good luck!