I have a Rack mount Netwinder that I had in place at a school, and I found it to be very limited.
The InfoPlace program was nice (as was the discussion groups), but in order to upgrade to the latest release which includes better security controls, you have to pay a fee.
The unit (even with 128 meg of RAM) was never very fast. Because the ram is soldered on the motherboard, it just means I am stuck.
Rebel.com touted the device as a print server. What they neglect to tell you is that it will only spool jobs for printers locally connected, not ones with their own ethernet interface.
The interface for setting up shares was very minimal, in that you had to have some basic knowledge of the Linux directory structure to create new shares.
On that same note, the manual and the device seem to go back and forth from coddling the user too much, to not at all. The DNS and Firewall pages are good examples. If the user knew the implications of what changing those settings would do, they would not have bought a Netwinder anyway.
Another company is yet again trying to revive the Netwinder with a new revision of the OS and a Transmeta processor. I wonder if it will be any better