I actually sold my Z-1 for the same reasons.
Korg boards are generally pretty heavy.
I'm OK with programming though.
Check out the Yamaha EX7 (not DX7). It's got good sound, it's easy to edit and it's got very nice keyboard action.
I also find Roland XP50 pretty light and easy.
BTW Are you lookin for something with the full size keyboard?
Does it have to be a synth, or you're OK with getting just a controller.

-ED-