What's wrong with 'UI designed for a touch interface' as a negative? If tomorrow an OS came out with a UI designed to be operated by a pair of sticks, and someone listed that as a bad thing, would you have an issue with it too?
Majority of pc's today don't have touch. They won't have touch for the next 2-3 years as well (remember, we're talking about pc's not tablets, and not everyone can afford or will upgrade to a fancy touchscreen ultrabook). Win 8 is designed to work best with touch, they've been very specific about that design goal. That's reason enough.
The details have been hashed over in countless threads. For every issue someone will list an alternative or simply say 'its not that different, you just don't like change, MS had to do it' etc. That's not productive.
Your example is ridiculous (why not go all out, and talk about a UI that requires castration?), BUT, if you could quantify the only metric of UIs that matters, AND, a stick operated UI had a better score in this metric, then yes. But it is not remotely possible that stick operated UI would score higher at any meaningful metric than the typical UI inputs. You're basically asking two questions at once, can a stick operated UI be better, and would I use a better interface, but combining them into some Frankenstein pseudo-question, where there is no right answer, and then acting like this has anything to do with Windows 8's UI. Anyway, that is not the case for a 'tablet UI', it can actually be better, some people have their opinion, but I view the program launcher (e.g. start menu and start screen) as having one meaningful metric; how painless it is to launch apps - and a UI that takes 2 clicks to launch all my programs is better than one that takes 2-5, with the average being 4, at this metric. Now that I've met our analysis quota, we can return to the regularly scheduled "Windows 8 TABLET PHONE UI SUCKS!@#" programming.