For me it's separated into two clearly defined categories.
The first category has the people that don't really care about what they type on, but the keyboard needs to have loads of extra features like lights, macro buttons and media keys.
The second category has the people that want a different typing experience with the added feel of quality, and who don't need a whole lot of extra features.
There are of course a bunch of nuances in between and around those two categories, but that's how I see it at least.
For me a mechanical keyboard destroys the competing scissor switch or rubber dome keyboards. I've been typing on the Apple wired keyboard (MB110LL/A) and it is a really nice keyboard for sure, but when i finally got to try a smaller, more compact keyboard with blue switches I couldn't imagine going to anything else again, simply because I finally feel like I am typing again.
This whole experience could be attributed to this being a new keyboard type for me, and the novelty might rub off the more I type, but only time will tell. Right now at least, I am having way too much fun typing on my new "baby".