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I also find Unity great. As a matter of fact, I don't think there's an easier DE for newbies. At the same time, it's one of the fastests for powerusers (look ma, no mouse!).
It definitely needs polish, but I'd say it's been getting it at every new release. By the next LTS will probably be a very solid one. I'm only waiting for the end of the (very stupidly justified) forced hidden menu to declare it the best available DE.
I must say I haven't tried Gnome Shell but for a few hours. It looks very elegant (it's visually MUCH better than anything else, IMO), but hide and seek is not my favorite UI paradigm... GS has a SERIOUS problem of discoverability. I know it can be heavily customized with extensions, but the approach isn't solidly backed by Gnome developers (breakage and discoverability of extensions is a weak point). I'm surprised no distro is offering Gnome Shell customized yet (Mint doesn't count; Cinnamon is not just a collection of extensions.)
I expect Unity to allow for a less "colorful" launcher, an option to show menus permanently (it's been coming for two releases already) and much more customizability in general. I understand all of this is planned to happen at some point, so I'm strongly behind Unity.
The fact that a company is behind Ubuntu brings some peace of mind too, since I must install it to customers, not just friends. (The Red Hat desktop is a second class citizen at Red Hat. The company is clearly server oriented. That's why I don't even think about it.)
So Ubuntu is the best distro out there for me.