Actually only XBoxes with Thomson drives (yeah...THOSE drives) had those rubber pads. Neither the Phillips nor Samsung drives have them. And now whoever makes the 360 drives (Samsung?) didn't use them either.
Again it comes down to cost vs benefit. It's obvious that after their experience with this XBox Microsoft is trying to save money wherever they can with the next XBox (even to the point of considering dropping the hard drive entirely). Unless they can get SATA and Gigabit parts for the same...
Because it won't be a client for a fileserver, it will be either an internet client (which most of the time doesn't even approach 10Mbs) or networked to other XBox2s in a LAN. And if a game needs gigabit speeds for LAN play, then I think the developers need to seriously optimize their netcode...
That's up to Microsoft to decide, but I seriously doubt they'd decide to add Gigabit even if it only costs them only a penny more. This is a game console, not a file server. Even the 100Mbs/sec that the current XBox has is overkill.
And if it is $1 extra, and they sell a million XBox2's at a loss, that's an extra million dollars that they lost. Do you think they're willing to take that on a feature that's pretty much unecessary?
Sure, the price difference may be small, but that's for a single unit. Multiply that price difference by millions of units and you'll see why Microsoft might not want to add something unless they feel it's absolutely necessary.