I bought this a fortnight ago for over £600, sent my invoice and barcode to Netgear and received my additional 2x 500GB drives today. Saw today that Misco have it for £546.23 including the cheapest £4.99 delivery option. This is the cheapest I have seen it from a site 'authorised' by Netgear, thus guaranteeing the rebate.
This is a lightning fast Business class NAS, but is also the perfect for media server, which is what I use it for. Usually this unit costs around £550+ EMPTY, and that is the lesser specced 'Pioneer' edition. This is the full spec Business edition already populated with 2x 500GB drives, and you get two more with the Netgear rebate, due to end 31st December 2009:http://www.netgear.co.uk/freedrives_nvx.php
Also this unit can be expanded when using Netgear's XRAID-2 option. Essentially you could gradually expand the drives to 1TB or 2TB units without needing to reformat. There are many online reviews rating this as one of the best and fastest NAS storages available (Trusted Reviews and Small Net Builder are a couple of sites). Sure it is pricey, but it is an AMAZING piece of kit.
A lot of people are raving about the ReadyNAS DUO deal, so I thought there may be interest in a much, much faster, more expandable unit: http://www.hotukdeals.com/item/537741/netgear-readynas-duo-rnd2000-134-99