Lion seems surfacy because that's the only thing they showed, but remember, "Instant on" apps, that necessitates a lot of under the hood improvements and one of those is a new file system. Yes, Apple could get away with HFS+ for Lion also but the next one it's guaranteed to change the file system. Even if they use SSD as standard in 2011 Macs the current file systems have all been developed for mechanical drives.
Can you imagine what would happen if Apple would develop a file system with SSD in mind? I can almost hear Steve: "The problem with the old file systems is that they are OLD, and they are just not good enough to handle the new technology drives!". 🙂
From the preview it is clear that Apple want's Lion to be a revolutionary step and not evolutionary therefore it needs a lot of under the hood improvements even if we can't see them yet.