[ugh]

I would recommend you get the DMG inside the Lion installer app and put it on some bootable medium (DVD, USB drive, …), that way you don’t have to worry about it.

Here is where you can find it:

Open up the Lion installer app bundle and go to Contents ▸ SharedSupport. InstallESD.dmg is what you want. Copy it somewhere. You can create a bootable install partition with Disk Utility.

I’m also gonna do that, if only to have my peace of mind. I guess I would prefer it if Apple gave us some way to just download the DMG but what they have done is pretty much the next best thing. (The whole installer app is, in fact, only a thin wrapper around the DMG.)