As far as video playback is concerned, the newer pxa270 chip with the iwmmx makes all the difference. With the proper kernel and player (Cacko 1.23, or Tetsu special kernel + iwmmx mplayer) I'm getting 640x480, 24fps, stereo video. This is the first combination that I've been able to use un-rotated and un-re-encoded (ie - meant for desktop) video on the Z. The newer clamshells blow the older ones right out of the water.
I've tried the same 640x480 video on both the 860 and 1000 - the 860 got maybe 5-8fps. The 1000 played it at essentially full speed.
Re-encoding and rotating the video produces smoother results, but isn't strictly necessary.
For all other operations, the 1000 and 3100 are basically the same speed as the Cx60s. The 3000 is a little slower because of its reliance on the microdrive.