Yeah, I really like the separate buttons on the T4x/T6x series. Don't really like the feel and tactile feedback for the mouse or keyboard on the T540P. I understand its probably cheaper, but I like the old thinkpad keyboards over the ones in the T430/T540 series.
I have a T43, aT510, and a L530. They are quite different, even though they look like twins (except for the width). The T510 has the old style touchpad setup, like the T43 has, and both have a setting in the BIOS to turn off that #$%^ touchpad (whoever invented that, should be shot). Each has a separate set of buttons for the touchpad, that are disabled when the touchpad is disabled in BIOS. The other set of buttons still work (don't know why they have two sets, within a short distance of each other). The L530 has a new style keyboard (which I like), and a new touchpad. It looks the same as the T510, but there is no BIOS setting to turn it off (again, somebody should be shot). A stiff piece of cardboard, taped over the touchpad (including the buttons), makes the machine usable. In all cases, I use a wireless USB mouse, and they work properly, with AMouse.