Firewire is an absolute MUST for me. I have a $400 Firewire 8-channel audio interface that is my home base for audio recording, and I'd rather not have to sell it. Unless they either have a light peak -> Firewire converter on day one, I'm out of the camp that will be able to purchase this thing.
Secondly, I'm going to need to instantly upgrade to a 500GB drive to hold all my audio VI samples. Obviously, that means no SSD (thankfully, doesn't look like it's going to happen). As long as I can swap out what measly drive they put in there with a 7200rpm 500GB, I'll be happy.
Third, it would be NICE if they kept the optical. Not a requirement, but nice. First of all, I'm going to need to re-install everything once I swap out the HD, and to do that, I'm going to want DVDs. I also have a 13+DVD Library of audio VIs that are going to be a PAIN to install if I don't have an optical.
Best outcome: they introduce Light Peak AND keep the Fire 800. Or they have a cheap Light Peak -> Fire converter out on day one.