I won't rehash what everyone else said - there are good reasons to buy a GP2X now but there's a strong case for waiting, too. Especially if your budget only allows for one or the other.
Here's what I've laid out so far on my GP2X F200. I'm in Australia.
GP2X $229
Carry case $29
AC Adaptor $29
2x 2GB SD Card $50 (25ea)
4 batteries & charger $70
Total $407 AUD. (I could have done it cheaper but I went for quality, especially with the batteries).
There will be no silly battery & charger purchase necessary for Pandora. Unconfirmed chatter seems to be that it will come with a TV out cable, something that would cost me further $18 for the GP2X. With all its power and potential, Pandora is looking like mighty good value.
Our dollar is strong against the US at the moment so I'm expecting a price of $350 AUD. Add anything from $20 to $50 for postage from overseas, and you're still in value country.