I'm looking at the Fostex 8 track, but it seems some are discontent because they don't get enough time on the 128 card that comes with the unit. They're all buying 256MB and 512MB cards. The 256MB is around $70 the 512MB is $100 to $150. Other than that they seem happy.

Some also complain about the effects on all of the models. But it seems they play guitar and looking for guitar effects. With a keyboard, since the effects are built in, that shouldn't be a problem. And I would assume the reverb would suffice for vocals.