OK, I've been through the various sticky threads, and I've added numerous tweaks and useful apps to my new phone. But there are a couple of things I need that I haven't figured out yet.
1) There are a few things that I'd like to be able to do quickly and easily, without a bunch of extra menus: a) Locking the TP2 and blanking the screen, b) turning bluetooth on/off, c) turning wifi on/off, d) switching between ring/vibrate. I know that I can set up the end key so that I can press and hold it to get either A or D (at the moment, I have it set for Lock), but that leaves the other three unaddressed.
I also know that there is an app that will let me remap a lot of the stuff on the TP2, and that may well turn out to be the best solution. But I'm going for something simple here if possible. If there's a simple way to solve these, I'd prefer that.
Go with the Rhodium Keyboard Controller. It will do a lot of what you're asking, and stuff you haven't 
I don't think you'll be disappointed.
2) On related note, under All Settings then under the "Buttons" setting. It lists six buttons, the first of which is "Send Key/hold". That is set to Voice Command, which seems reasonable. But the other five buttons are just listed as "button". I have no idea what they do. Is there a way to make them map to actual or virtual buttons on the device?
Hmmm, I only see the one button for VoiceCommand. Yours must be carrier specific and I'm thinking those buttons are still there from a previous device that had a lot more hard buttons...like the Mogul.
3) There is a tweak that lets you record calls. The record option shows up on the call menu. But where do you go to play back the resulting recordings?
It actually records a voice note, so launch the Notes app, or look under My Documents\Notes for the .wav file(s).
4) Where is the battery gauge? I can see the battery state on the Battery settings screen, but isn't there a way to easily see it from the Home screen?
I don't have a stock taskbar anymore, but isn't there a gauge next to the HTC Task Manager on the right? Failing that, checkout some of the taskbars in the Touch Pro 2 Tweaks, Hacks, Tips & Modifications thread. I use the one from the very first post by Mighty and it works really well...
5) Can I change the soft keys ("Camera" and "All Contacts") on the home screen?
I haven't read it, but hopefully this thread might have an answer for you.
6) Is there any way to add new tabs to the UI? For example, could I add an RSS page next to my Weather page?
Can't answer that one sorry, I don't use TF3D.
I'm sure I'll have other questions over time, but those are a few that I haven't yet found answers for. Thanks for any help!