Correct, USB only. The USB acts essentially as a cradle -- you HotSync to it as you would any Palm, or you can use it as an emulated serial connection which is what I'm doing for PPP.
It does have wireless, but I have a locked-down WiFi install on a DMZ and the Dana doesn't speak WPA2. Unfortunately, you can't connect Ethernet to it otherwise (I tried four different USB Ethernet dongles and the Dana wouldn't recognize any of them), so PPP-over-USB is the only practical means of connection if you don't have wireless. Well, I suppose you could string up a modem, but I don't have a phone line anymore after the T1 took both pairs and stringing up a terminal server just for the Dana seems a little silly.
I have a Z88 in my collection too. They are neat devices.