There are some things I "like". Like Ultegra 6703, XT Dyna-sys. Yokozuna Reaction cables. Both bikes go up hills a lot, and I like both bikes to stop and shift crisply.
Frames on the other hand are quite different, and that's where I'm interested in the different character.

On another bike I have bar-end shifters and they just annoy the crap out of me. Some day I'll have brifters on that one too.

I guess my personal point of view is that most of the time I'm not trying to ride a different bike. Instead I'm trying to ride a different route, and the route wants a different bike.