Hi,

Happy Kurzweil PC3x owner since April 2008 (first tried to place my order on 27 Nov 2007).
Playing various stuff -- piano+pad+strings+bass parts on softer songs, organ/bass on uptempo, faking solo electric guitar, orchestral pieces with wind solo parts (with breath controller), triggered drum riffs as backing track + funk bass + epiano, left hand upright bass + velocity triggered drums + right hand jazz piano, comp+soloing over completely sequenced drum track songs .... It's been really versatile.

My rig has expanded a bit since then, although I've found no reason to consider replacing the PC3x:
Kurzweil Kore 64, ribbon controller, FCB1010 floor midi pedal controller board, Ventilator leslie, old Yamaha breath controller.

Played the other "big" boards an afternoon in a store a month ago. Biggest difference is clearing display and UI technology taking a leap forward since 2008, but sound-wise -- no reason to upgrade.