[quote name='warlock7']Hmm wondering whether to get this or the 20 GB. This will definitely be worth it if it is the new chipsets or something extra rather than just the 40 gigs.[/QUOTE]
Don't count on the new chipset, as in the past with 360 HD size has never matched up to chipset change. I'm sure sometime in August-September we will see a trickling out of new chipsets, but it will probably be slow and inconsistent just like when Falcon rolled out.
But otherwise 20gb vs. 60gb is a fairly simple decision based on one thing:
How much content do you download?
First, if you download a lot of those 800pt expansion packs from Marketplace, they can take up quite a bit of room. If you generally just buy games from retail stores and arcade and generally don't download too much extra crap for them, the 20GB will be fine. Most XBOX Live Arcade titles are 40mb-50mb in size, though there are a couple of 100-150mb ones. Big expansion packs like the ones for oblivion can take up to 5GB, while smaller ones for titles like Rainbow Six are only 500mb-2GB. Consider that the 20GB drive has 6gb reserved for cache usage (14gb usable), and you can see if you are downloading a lot of these extras the 20GB will be cramped. But if you are the typical gamer who doesn't do a lot of online downloading the 20GB is okay; myself, I would need the 60GB.
Second, you should consider whether you plan to use the XBOX Live Video Marketplace - will you be downloading movies & TV shows to watch on your XBOX? If so, I'd spring for the 60GB as feature-length 720p movies are 4-7GB in size each.