Ian,

A friend of mine,as well as a long time pro musician, purchased one thru Frankieve. He bought it for playing with his quartet or big band. He won't take it to smaller 1 hour nursing home gigs ( too heavy).

I went to his studio to play the board and give him some pointers on setting up Songbook. I spent about 15 minutes playing it as a piano, the rest of the time was walking thru some of the basics of the OS. Not sure how much valuable info I can give you based on playing it for such a short amount of time.
Anyway here's what I thought. The action is a terrific weighted action. If I were mostly playing piano solo gigs but wanted features of an arranger this is the one I'd own. Not sure what your friend is going to use it for but the polyphony seemed a non issue, again 15 minutes playing it wasn't enough to put it's thru it's paces. It has many similarities to the PA800 and Pa2xpro. At it's price point the pianist gets a lot of bang for the buck.

I would not trade my Pa2xPro for a PA588.

Pros of the PA588:
Great 88 weighted keys
Dual sequencer
Songbook
Built in speakers

Cons:
Monochrome touch screen
No USB host
Proprietary power adapter
No input jack for use of the EC5 pedal

Hope that helps. One last thing, I think it certainly is worth a few hours drive to try it.