The kind of person that picks up an Android phone is tech-savvy enough to handle manual file storage. I like it, actually, because it lets me use my phone as a flash drive.
Regarding app data, from the Gizmodo liveblog:
They store apps in the internal ROM and not on the SD card now, for piracy reasons, but they will offer an upgrade soon for installing apps on the SD card.
That's why they're still a niche player- it's far too much about techies and open source fans right now, and that will poison the App Store selection moving forward for the mainstream.
Regarding app data, from the Gizmodo liveblog:
They store apps in the internal ROM and not on the SD card now, for piracy reasons, but they will offer an upgrade soon for installing apps on the SD card.