Samsung Galaxy Tab 10.1 - If I apply the update and install TouchWiz, will it hurt me?
Well, nobody seemed to be able to answer this question, so I went ahead and applied the update.

Overall, I'm glad I did. I haven't noticed any significant change in performance. I could take or leave most of the UI changes included in Touchwiz, but there are a few things in the new UI that are very nice. One is that toggles for things like bluetooth, wifi, and auto-rotation are now immediately accessible in the notifications pop-up when you touch the notification tray. Another nice thing is a dedicated screenshot button that appears next to the regular android buttons in the control bar at the bottom. Press it at any time for an instant screenshot.

I haven't noticed that any features have been disabled. I don't have a 3G-capable tablet, so I don't know if the "portable wi-fi hotspot" functionality would be affected by the update. But everything else I've tried functions as it did before.

Also, an unexpected bonus to the upgrade is that Samsung released a bunch of new apps bundled with the new UI, some of which are very useful. The ebooks app especially is nice for me, it reads EPUB and PDF files, and it formats EPUBs better and performs faster than some of the other apps I've tried (like FBReader). There's also an app for making adjustments to photos, and a few others that I haven't really used.

The new TouchWiz UI also includes a handful of mini-apps that can be launched from the android control bar at any time. These apps appear in small windows that float over whatever other apps you're running, and they can be moved around. None of these apps are really awesome, but some are useful. For example, you can bring up a mini-view of your calendar, a small music player, or a note pad you can type into or draw on, without leaving the app you were using before. It's kind of a neat idea, although I'm glad this isn't a standard android feature or there would be way too many apps written this way, and Android would lose a lot of its ease-of-use.