As far as I know, there isn't yet a good, inexpensive, well-documented ARM system. I tend to prefer the Marvell Kirkwood systems (the plugs) because they have faster processors, faster and smarter Ethernet controllers, and somewhat simpler SoCs than the TI OMAP3 systems (beagle, igep, gumstix). On the other hand, the video controller on the openrd is effectively undocumented and the guruplug display isn't yet available.
The beagleboard is a mistake: its lack of real Ethernet is a major failing, plus we haven't been able to get OMAP USB (EHCI) to work yet, so one can't even use the kludge of USB Ethernet. We have video working on the gumstix, but without working USB, there's no way to attach a local keyboard or mouse.
