I haven't really switched but added Pentax as my travel gear. My current Canon gear is full frame including my film system, yes i'm a diehard film guy
What i've noticed; nothing,other than ergonomics, menu and higher price on Canon related gear Pentax gives me the same images i want for less. (matching newest models)
I bought into the K200D, i get weather proofing on what they call "entry-level" because the industry considers pre-sets on the dial "entry-level", well take a look at some "pro" models where you can pre-set in their menus albeit not on a dial
Also you can buy into some real nice weather proofed lenses rather inexpensive compared to the industry standards. (their entire line is priced for the value conscious, not a bad thing these days the way the economy has gone)