Integrated storage slot
The integrated storage SD slot (accepts SDHC) is used by the file system as it gets mounted into your home directory, which is itself in the /mnt directory. It's a *nix thing that M$ pinched in Win 2000 btw.
I bought the 150 L last week and I'm using it for nearly everything although you will definitely want to change the default twit-proof interface to something more flexible - acerguy will tell you how.
The 120GB holds my MP3 collection (60gb) and still has space for a few movies for the kids although you really want a power socket for movies.
For the record, everyone who has seen this has asked if it is a "real" pc, they are quite surprised when I tell them that it is.
Will buy an aftermarket battery when they come down in price, unless I can source some good quality li-ion cells and build one myself.
Run on alkalines, not very green is it! Now a solar case lid, that would be funky.