GottaBeMobile has a very good post on the pros and cons of buying the Nexus 4 now or waiting or the Galaxy S 4. It's a very good post for those who can wait until the Galaxy S 4 is out and for sales.
For anyone else, if you need it now, you can't go wrong with the Nexus 4. I'm just very satisfied with the stock Android.
And if you're gonna wait, you might want to throw in the Xperia Z, which is not likely going to make to the US and HTC's M7. Oh, and let's not forget Google/Motorola's X phone.
That is if you can wait.