Engadget just posted a pic of the inside of the mactels they are just g5 tower cases though they appear to be much more roomy without the g5's in there.
Just so you know, you don't get the hardware discount until you *renew* your Select membership the second year. So, you have to pay for two years @ $500 per year before you get a developer hardware discount (%20). I used mine last year to purchase my 2.5 GHz G5.