Pocket PC's come with a limited memory for MP3 compared to the 20/40 gig iPods, so it depends on what you want. The 20 gig model is enough unless you have a music collection that exceeds most - and some of the add-ons are fantastic.
However if you want one for Christmas you should have ordered it last month, you'll struggle to find anywhere that can deliver now in time. Looks like its going to be the number one present again!!
On a side note to the original question does anyone know how compatable iPods are to Windows XP? I have all my music stored with Real Player as .ra files and don't want to change them all to MP3 and downgrade the original quality. Is it easy to download into the iPod from the .ra files and convert as you do so or do I need to change all the existing files?
Hope this helps and thanks in advance