I've seen those adapters, but I'd prefer to use only one SD card and a simple (read: less likely to have weird edge-cases) adapter. But I haven't taken the plunge myself either, mainly because high-capacity SD cards are still pretty expensive.

I think RAM will be less of an issue for me since I run Rockbox[0] on the iPod. No need to keep the whole database in memory there. I like everything about the iPod except the software (pretty much the same as other apple products :)

[0] http://www.rockbox.org/