I've been typing on a Model F AT and Model F XT side-by-side for a few days now and I wanted to post some differences between the two keyboards in terms of typing feel. I've seen many people claim that they feel different to type on (AT vs XT), so I figured I'd throw my 2 cents into the ring.
-The AT has a slightly lower pitched sound. This most likely has to do with the chasis of the keyboard. The AT is 100% plastic whereas half of the XT's chasis is metal.
-The XT has a much rougher texture to the top chasis than does the AT. This texture is somewhat noticeable on the palms of the hands, but by no means uncomfortable.
-The XT feels a tad lighter to type on (but this could be due to a number of variables having nothing to do with the keyboard itself...such as how the keyboard was stored, condition of the springs post-storage, etc.). What I mean when I say "light" is that the XT requires less force to buckle the spring and actuate the key switch.