I think everyone's words have just disappeared into a next generation war... nevertheless here's my input.
I'm a Wii owner. I'll go through its bad points first:
The games are definitely too short. Example- Metroid Prime 3. I completed the game 97% in about 15 hours. To get 97% in MP1 or 2, that would take well beyond 50 hours. Bummer considering MP3 is one of, if not the best games out on Wii at the moment.
The sensor bar is too short. I could barely play my Wii from the end of my bed... until I spent $30 (Australian) on eBay to buy a sensor bar that reached 7m back. It's awesome! But is everyone going to jump on eBay for a new sensor bar? Probably not.
The quality of Virtual Console games is pretty meagre, except for maybe one or two good ones Nintendo releases about once a month. On the same topic, the games are terribly overpriced points-wise, and the points cards (in Australia, at $35 is far too expensive). Though the good games on VC are brilliant. I just got Pokemon Snap the other day and am loving it. Other great ones include Lylat Wars, Kirby's Adventure (for something that's not N64) and Donkey Kong Country 1 and 2.
Graphics-wise, they don't measure up to the 360 and PS3... but do I care? No. You have quality games in Super Paper Mario, Mario Galaxy, Twilight Princess, Prince of Persia (though a port, is much better with Wii controls)... and fantastic gameplay in games that aren't so mainstream such as SSX Blur.
That's really all the downsides I've noticed (and can think of at this time). On the upside however, I've found this:
Game quality is really really good! It's a point I can't stress enough. That is, most games released by Nintendo. Someone said before that Nintendo needs to let more third party companies develop games... well the truth is that most (but certainly not all) third party games are plain terrible. Metroid Prime 3 is one of the top games on Wii and companies should take a leaf from Retro Studios' book when considering making a game for Wii. Nintendo games to reiterate my point are great and I mentioned some of those earlier. There are plenty more, to quickly mention though not having played: Brain Training, Mario and Sonic at the Olympic Games etc
Likewise, Virtual Console games, when there are good ones... they are good! I have fun taking a break from my Wii games to play the classics! Pokemon Snap even has Photo Channel capabilities where you can save a picture from your file and post it on the message board where you can edit it and have fun with it etc. Which brings me to my next point...
The extra channels on Wii provide a good means of sitting back from games and getting a new edge out of your console... if you have internet. I check the weather almost daily, catch up on headlines every morning and submit Mii's in the Mii Competition Channel. Alright, the Everybody Votes Channel is pretty bull, but plenty of people use that too! You can chuck your music and photos onto the Photo Channel (what's with the AAC files? huh?) and view slideshows and have fun with them, or browse the internet on your television. On a side note, you can stream your music and videos on the Internet by downloading a program called Orb on your home computer... google it if you're interested! And the Mii Channel is pretty fun and funny too.
Backwards compatibility with the Gamecube. Every game you had on the Gamecube is compatible with your Wii. Right down to the control and memory card! Neither the 360 or the PS3 (anymore) have full backwards compatibility, only allowing you to play the more recent XBox and PS2 games. It's great still being able to play Mario Sunshine and what not.
People have been saying the Wii Remote is gimmicky and only lasts a few hours. WHAT?! It's comfortable, it can be used in so many different ways, with the nunchuk, on its own or on its side. Super Paper Mario was a fun game to play on its side, so was Sonic Secret Rings (though not to the same extent). Metroid Prime 3 works so well because of the controls, as does Mario Galaxy, and Link's Crossbow Training, a fun demo game is fun to play with or without the Wii Zapper attachment. Though not played it yet, I can imagine Resident Evil Unbrella Chronicles is amazing with or without the gun-like attachment (great reviews by the way).
You can play standing up or sitting down. If you're on your own, you can play relaxing on your couch or, if you're like me, lying on your bed, exactly like playing with any other console. With friends, it's fun to really get into it and play standing up (Mario Strikers Charged, Wii Sports anyone?).
There's plenty more you have to really discover for yourself. It's impossible to say you hate because your friends hate it. The Wii is both a personal and company-inducing (?) console, and everyone finds their own likes and dislikes about it. It's not something you can judge of playing for one hour. If you don't like it after two or three weeks then sure, it might just not be for you. With Wifi and DS capabilities though, I reckon it's something you'd have to hate so much before you'd be ready to return it.
Having said all this, I am a big fan of the 360. It's heaps of fun and thoroughly enjoy playing it at friend's houses. And another selling point for the 360 is that, despite many of its games are out on PC, not everyone has Vista and probably won't upgrade to Vista for quite a while... I won't. I haven't played a PS3 but truthfully I don't really want to and I'm doing just fine without. Maybe when more games come out, the price comes down more and they make the hard drive bigger again and have full PS2 compatibility (is that ever going to happen? no), then I'll get one. One plus I hear about the PS3 though is that buying it is cheaper than buying a BluRay disc player... but who needs BluRay? Movies are just fine on DVD geez...
That's my two cents... or two hundred rather.
Jono