Ive been in all 3 camps, I was continually underwhelmed by Canon... bodies, glass, everything, and they're the biggest footprint in DSLRs. Jumped ship happily to Nikon, and only consider picking up a Canon body for the new TS lenses and alt lens adaption.
Nikon is great, world class glass, and the bodies are nice, but for me, you just don't get enough bang for the buck out of the bodies resolution wise... for what I do at least. D700 high ISO is great, but Low ISO isn't the best, and the lack of rez makes all the great Nikkor lenses sad.
Nikon's high end lenses aren't any cheaper than then Sony Zeiss/G counterparts.
Sony has been able to meet all my needs, the glass line up is world class quality, simply phenomenal, though does need a few things here and there. It really isn't as lacking as you might think. Even if you only consider current Sony lenses. Really all I am missing is a fast wide like a 24 1.4 and a really good fast 50 (the current offerings are fine but not amazing), but G or Zeiss versions of these should be coming in the next year... outside of those, what's really missing besides the long teles and TS lenses?
An a900 and the ZA 24-70 cover most of my needs, then for low light / portraits the Zeiss 85 1.4 and 135 1.8 are just insanely good and worth every cent.
I'll also add the Sony flash system is just awesome. A pair or trio of HVL-F58AM flashes and some stands and you have your studio lighting down.
That said I can't recommend the Sony system enough. Go for it!