I wish that all Android phones came with an option to have stock UI or the add-on UI. From what I have seen the only one that really adds anything to the experience is the Sense UI the Motoblur and the Touchwiz are pretty damn useless.
While I agree that we should have the choice between stock and a customized UI, TouchWiz enhancements goes beyond the launcher (which i suspect is the responsible part of much of the hate) and UI. They just aren't mentioned as prominently as HTC Sense's features.
These include:
GPU accelerated browser
Puzzle Piece lockscreen that lets you jump into your missed calls, emails and texts if you have them - a shame they decided to get rid of this for TouchWiz 4 on Galaxy S II
Social Network homescreen and contact integration a'la Sense's Peep and FriendStream
Swipe left/right to text/call from contacts/call log
Notification Shade toggles
Inertial scrolling throughout the OS
AllShare DLNA support
File Manager built in (not as powerful as Astro but gets the job done for most)
Task Manager that's "safe for n00bs" by hiding system apps that can break by being closed. You'd be surprised how many non techies feel the need to "close" all the applications in order to make the phone "feel" faster. More advanced users can use the standard Android settings menu to close more applications.
There's more but I'll have to take a look at a Galaxy S phone some more, and it's not to say that TouchWiz 3 is without flaws: For example, the spelling and grammar issues in some less traveled parts of the UI are hilarious at best, but maddening at worst when you consider how much you're paying for the product. It's shocking that Verizon of all the carriers who got a Galaxy S variant didn't catch this on the Fascinate.
Blur, at least the new version of the Motorola Application Platform (the Blur that's on the Gingerbread Moto Droid phones) looks to be getting a lot better. I still don't like it as much as TouchWiz or Sense, but i have to play with it.
Wasn't aware of that, how?
Download a launcher replacement from the market, like ADW or LauncherPro, then hit the home button once it installs. You can then choose which launcher you want to enter and then check off the "always open this.." box on the dialog to map the home button to always return to the launcher you want.