>Why change brand though?
I'm not interested in changing brands. Not right now and not anytime in the foreseeable future either. My last post was in reply to the "too invested to switch" argument that I hear in almost every photography forum nowadays. But it was all hypothetical and in the spirit of the subject of this thread which is "what would make you jump ship?"
For me, my first DSLR was a Canon XSi (as a kid I also dabbled with my mother's Ricoh any chance I got but that doesn't count now, does it? ;p). At the time I bought the XSi, I didn't have much brand preference but was leaning a tad bit towards Nikon. However, a friend of mine who shoots Canon was upgrading to a 50D and offered to sell her XSi along with a couple of lenses for a very good price so I took her offer. I figured I could always sell the XSi if I decided to switch later on but I actually ended up keeping it and now I'm even thinking of getting the MP-E 65 for it (but that's another story hehehe).
Now, I'm not trying to say that selling an XSi with a couple of lenses is like selling all your equipment when you invested a few thousands in them. That's not my point here. My point is that after the XSi, even though I loved it, I made the switch to Nikon but it wasn't because of any glass envy or better Nikon sensors or anything like that. It actually was because of the way I felt about Nikon as a company.
First, Nikon never changed its lens mount. This is huge to me because it tells me that Nikon is committed to their product and willing to work with what they have and modify it to fit their need instead of quitting on it when it becomes limited. Another thing is that Nikon USA offers a 5 year warranty on lenses and that says confidence in their lenses. One other little thing is also the inclusion of the hood and the lens pouch/case with every lens. That used to mean a bit more before Nikon USA rolled out their minimum selling price policy as Nikon and Canon street prices used to be very close at the time.
So you see where I'm going here? I kinda got into Nikon because of their spirit and much less because of their tech. Honestly, the only way I'd switch is if I see Nikon caring less for its customer base and more for its bottom line.