I would buy the Wii mini (especially if it's a completed boxed version) for $30, but just know what the Wii mini doesn't have: internet capabilities (means no Virtual Console / Wiiware games as well), 480p output, SD card support, Gamecube support. If none of these matter to you, then by all means use it as your primary until you upgrade to a Wii U down the road.
Personally, the biggest let down of the Wii mini is the lack of 480p output, as even though the Wii is weak in terms of graphical power, tethering it down to 480i makes it that much worse on a larger HDTV.
Again, I would still buy it for $30, if not only for the red Wii remote / nunchuck combo and the Wii mini console as a collectable in the future.