As a sideline, I brought home one of our battered iPAQs and flashed it with Opie 1.0. It's definetly not what I would call a "consumer" PDA now (and the model I'm using doesn't have much RAM or Flash), but it should help with a few tests we're running. As soon as I can get the bloody drivers to work properly, of course.
I'm still convinced that Linux on a PDA is a stupid idea, but at least it's becoming easier to install (just dump the files on a CF card, click on a few things, and presto). This particular device has already run Windows CE 3.0, Pocket PC 2002, Linux (bare X11), QNX and Pocket PC 2002 again, so just dragging and dropping files around instead of uploading 8MB via the serial port was a very welcome change.
Update: Wi-Fi support with the base image ranges from good (auto-detection and configuration of Cisco, D-Link and Agere-based cards) to hideously lacking (non-broadcast SSIDs and some WEP keys can't be configured properly sometimes, with no discernible cause).
I've had to remove nearly all PDA functionality to get the packages I wanted to install, though, so I won't comment on usability as a PDA other than note that it garbles vCards with accented characters.