The Dell Mini 9's for 1gb ram, 16gb SSD, 4-cell battery, Ubuntu linux, for $409.
The mini9 isn't available with a hard drive. But, you pop a panel off on the bottom, and you've got direct access to the three mini-PCIe slots and the ram slot. The SSD is in one of the mini-PCIe's and is thus trivial to swap out for something of equivalent size (apparently the eee's drive is physically too big). On the other hand, it does, optionally, come with bluetooth and webcam built in. I included those when I priced it out yesterday.
The Acer, on the other hand, is apparently a bitch to open and upgrade. Tho, with a 160gb drive, I probably wouldn't need to during its time with me. Another consideration is that I'd want to put linux on it, instead of XP home, and I'd want to run Ubuntu, and I'm concerned about drivers and other compatability issues.
Hm, I think I've just made the argument for the dell pretty well.