In order to install software on the MBA you have to install a special utility on one of your computers that has a DVD or CD-Rom drive. You then have to install software onto the MacBook Air over the network from another computer. It has to mooch optical drives off of other computers. ;) You could also transfer disc images over the network but with its small 80GB hard drive you are going to be running out of space fast. That's how big the hard drive in my Mac Mini is and I'm kind of hurting and I don't keep disc images on my hard drive or movies.
Oh, according to the video they have at apple.com they also have a thin external drive for it.
Oh yeah and one other thing.... it seems like they had disabled time machine over airport so they could come out with the new Airport called "
Time Capsule". The thing here was that the previous Airport Extreme didn't have a built in hard drive but people could hook up USB hard drives to it. This new one has an option for a 500GB one for 299 and a 1TB version for 500 bucks and is officially endorsed for Time Machine. I wonder what else they might have fixed compared to the older Airport.... or if it's just marketing.
The difference between this and the Windows Home Server though is a "Time Capsule" doesn't run a server OS and doesn't do more than file storage and backup.