Historically you could use OSX Server as a local update/patch server, and have other Mac's on the LAN use it instead of downloading the same stuff again.
They say they're making Lion Server free and easily configured, and I'm hoping that they're integrating the App store components as well.
Ahhh... I was just going by what was reported by someone at the keynote. Still, it's priced way cheaper than the previous versions, and I'd gladly pay the $50 for the convenience of a local patch/app server. (I have 5 macs in the house).
My biggest peeve is the download-only for the OS, as I have rather crappy internet access, and dread the thought of downloading a multi-GB update.
From my understanding of it the delta updates are only for the y part of x.y versioning, not whole point upgrades, and only for iOS. OS X already uses delta updaters and has done so for years.
They say they're making Lion Server free and easily configured, and I'm hoping that they're integrating the App store components as well.