I bought my wife a Mac mini about a month or so ago... base model (1.83GHz) and upgraded the RAM to 2GB with some spare RAM I had lying around (pulled from my MacBook that I upgraded to 4GB).
While 802.11g isn't the speediest, its fast enough fortunately for everything my wife does, and since Time Machine runs so nicely in the background, it doesn't matter how long it takes (though it does its thing pretty fast since she creates many small files; nothing huge at all). I have two separate wireless networks in the house - one N-only (via a 1GB Time Capsule) for my MacBook and the AppleTV (soon to be two AppleTVs) and one B/G (via an AirPort Extreme in bridge mode) for her mini, the iPhones and my kids' computers.
While I agree the mini is in need of updates, I'm happy enough with it for her (and it replaces her dual 2.5GHz G5 machine, and she doesn't notice any speed decrease whatsoever!).