The Nintendo WiFi dongle is a tremendous waste of cash. Its range is OK, but it's a proprietary system that only connects Nintendo devices and only when your PC is running, and they charge $50 USD for it. You can find a real wireless router (which will work with ANY device) online for as little as $20
That said, I love my Wii. I have a Ps3, and a decently powered gaming PC.. but the Wii is the only thing that gets any of my gaming time between Virtual Console titles, Rock Band 2, and Mario Kart. Then there's Zelda, Smash Bros, Wii Fit, New Super Mario Bros, Mario Galaxy, Wii Sports, Metroid, Boom Blox, Rayman Raving Rabbids, Resident Evil 4 remix... there is a load of shovelware out there for Wii, but don't let that take away from the fact that there is a huge amount of great games and experiences out there for it. The only people I don't recommend a Wii to are people who only like to play M-rated games, or FPS hounds.