Read The, um, Fine Manual.
I meant to say this in my earlier post about the Installation Guide, but please be sure to review the Installation Guide before you install Team Foundation Server.
First, some stuff has changed since Beta 2 and the July CTP. For example, we now use the same SQL Server for all Team System data - including SharePoint. We've also fixed a lot of the stuff that previously required manual workarounds.
Second, it's good engineering practice. The vast majority of setup failures I've helped to troubleshoot have resulted from not following directions. Yes, it'd be great if everything was so bulletproof that it just worked out of the box, but Team Foundation Server is not a simple, standalone application.
On my first day of sixth grade, the teacher distributed a two-page test that consisted of over fifty items. On the first page, it said to read all of the items before completing any of the items. The teacher then told us we had something like 15 or 20 minutes to complete the entire test. Of course, the vast majority of people dove right in and proceeded to tackle each item in a race against time. However, those that first read all of the items found that the true test was following directions. The first item was to write your name on the paper. The last item was to only complete the first and last item and skip everything between them. Of course, the other directions included steps that were sure to reveal those that had followed directions. For example, half way through the test there was a step to stand up and announce to the rest of the class that you were halfway done. Moral of the story - follow directions.
While you're at it, review the Readme and Known Issues, too. And since all three documents are available separately, they'll give you some reading to occupy your time while you wait for the bits to download.
A Lesson in RTFM...TFS Beta 3 (Finally) Set Up.