I have the Triton (61 keys). I like a lot of stuff about it, but there are annoying limitations that weren't made clear to be until after I bought it.
For instance, you cannot save songs internally; you have to save to a floppy (slow) or a SCSI disk (requires a $150 controller). If you forget to save before you turn the power off (or it goes off due to a thunderstorm), your song is gone. Ditto for samples.
Of course, if you plan to do your sequencing and sampling with computers or some other external gear, the saving issue won't be so much a problem.
I suggest you check out the Triton Central discussion list:
