Personally, I like the Unity interface. There, I said it.
Certainly it has been quite buggy in recent times, but that's the nature of Linux, things get released well before a company like Microsoft normally would so that the community can start to strengthen it.
I find Kubuntu to be clunky, and I really can't get on with KDE, whereas a recent release of Ubuntu (I personally use 12.04 LTS on all of my current workstations that I use on a daily basis) I find to be a very productive working environment.
That isn't too say that problems with later NVIDIA/ATI graphics cards etc. have gone. the built in Nouveau universal driver can really cause some issues (to the point where my work laptop with an NVIDIA GTX 580M in it won't boot unless I modify the GRUB boot line to disable it), I haven't had any problems on my other workstations that use GTX 6xx series GPUs, the "Jockey" driver application quickly and easily install one of 4 choices of driver and sorts everything out, installing the properietry driver is fairly easy now too.
I should say that, a few years ago I was an avid Windows fan, I really disliked Linux and Unix, but as my needs forced me towards them I tried quite a few but settled on Ubuntu, which was good as 11.10 but far better as 12.04 (not sure what 12.10 is like). Now the bugs are being ironed out in Unity I can honestly say that when I go back to Windows THAT now feels clunky, the text is too pixelated and I miss the smooth fonts and feel of my Ubuntu desktop.
Ultimately though you tend to get used to something and then when you change, it always feels clunky at first. If you use it for long enough because it doesn't bug you in any major way, then I think you often form the opinion that your choice is the best, whereas in reality it was probably the easiest one (like me with Windows when what I do is far more productive in a Linux/Unix environment) and you're simply used to it.
