Just a note from someone who is primarily a Nikon user...
Before jumping the fence because the grass is greener on the other side, you might want to remember that all manufacturers have issues with line-up and quality.
The top-of-the-heap APS-C for Nikon is still the D300/ D300s - with nothing other than rumors that they will see an upgrade. Some who shoot wildlife and such have been clamoring for an upgrade for a while and it doesn't seem to materialize. Some are not happy with the size or performance of the D7000. Some of them are thinking of jumping the fence.
Nikon still has minimal APS-C prime glass, and none at the wide end (have to use zooms or 3rd party). Pentax has the DA Limiteds if you want decent small and light primes.
D800/ D800E bodies are experiencing focus issues. Not all, but enough that it is a problem for Nikon.
D4 bodies aren't exempt either - there are people getting replacement bodies because their new D4 is not working properly out-of-the-box.
There are Nikon users threatening a jump to Canon.
There are Canon users threatening a jump to Nikon.
There are etc...
Every manufacturer has quality issues.
Every manufacturer has gaps in their line-up that their customer base may not be happy with.
Pros need to do what they need to do for their business.
Amatuers and hobbyists - we need to ask ourselves if the gear is the important thing? Or is it the joy of photography?
For me, it's the enjoyment of getting out and taking photos. I'm not that great at it (and am trying to improve), but it is an enjoyable activity for me. I'm not a fanboy, so I tend to use what I like and not be tied to any one brand. I currently have Canon for 135, Pentax for 645, and Nikon and Olympus for digital.
I
had a K-5 and DA Limiteds, and got rid of them in a moment of pure fiscal thinking (not wanting to support two digital camera systems). The right choice from a money stand-point, but at the cost of some of my enjoyment of photography. I have yet to find a digital solution in a crop format that fits my hand and has the quality of the K-5 and DA Limiteds. Now with Pentax's roller-coaster of pricing on it's lenses, it will cost me more that I may be willing to pay to get back to what made me happy.
So please, do a little evaluation of what makes you happy/ what you actually need before switching systems. It can be costly, and even moreso if you decide to come back.
Just the opinion of a hobbyist who jumped ship and wished he hadn't. YMMV.