My girlfriend and I have had the Wii for just over a year now. We got it with Wii Sports obviously, as well as Wii Play, Mario Party 8 and Super Monkey Ball. We sold Monkey Ball, Mario Party 8 is only fun with 4 players and I love Wii Sports.
At first, I wasn't that impressed with the console (but I bought it for my girl, not for me). After a week or two, I really got into the Wii and I started buying many games for it. Now I have Super Mario Galaxy, Twilight Princess, Metroi Prime 3, Mario Kart and Brawl as my favorite games, and I don't think I ever enjoyed a console as much as the Wii.
I look forward to Guitar Hero 4 (though I think I'll get that one for the PS3), SimCity Creator, Call of Duty 5 and The Conduit, among many other, more obscure (read: Japanese) titles.
But there are a lot of things that can be improved on the Wii. Most third parties still don't get the Wii and probably never will. Online is good enough for me, but still should be heavily improved (Brawl is unplayable online). Anohter minor annoyance for me is that I need to shut the curtains at the other side of the room when it's even moderately sunny, or else the Wiimote goes insane.
Overall, I'd give the Wii an 8.5/10 Pros are multiplayer, Nintendo games and overall fun factor. Cons are lackluster third party efforts and online functionality.