It's the same system, but the fob is bigger to accomodate for more buttons (remote start and all the door releases the minivans have)..
The 2009s will have completely keyless entry/go (you keep the fob in your pocket) - I hope they go for a credit card key, but it'll likely be whatever mercedes decides to use
Honestly there's no reason to buy a 2008 right now unless you get a killer deal - the 09s will be available without the gigantic stick antenna on the roof, and you might be able to order them without sirius (eg, NO antenna on the roof! SWEET!) just like my 06 is
Plus the keyless go
