With the new XBLA edition out many people may forget about the fact it is on the PC. In fact it is out on the PC for 75% off with the coupon blitz1 available to reduce the price again by 50%. So if you are interested in buying peggle but don't want to cough up 800MS points I would recommend getting it on PC. It should also run on virtually every PC/laptop going as well. Using this I managed to pick it up for £1.28 earlier which is much better than the XBLA price.
EDIT: I should have mentioned this is directly from Popcap's website