Though it's not perfect, the Wii version of the Guitar Hero III controller does the job just fine.
Plunking down $90 for a video game of any sort is a pretty big investment, even if it includes a game-specific controller. It's especially important to know whether or not the plastic Les Paul guitar that is bundled with Guitar Hero III: Legends of Rock is going to last long enough to be useful for when Guitar Hero IV (or Rock Band, maybe?) comes to the Wii. No one is going to know for sure until after the guitars have been put through a few months of rocking, but I can say that, much like the game, the new guitar is the best one yet. Still, it's not perfect.
First, there are improvements over previous Guitar Hero controllers. By far, the best feature of the guitar is that it's completely wireless. Besides being free of cords that someone might trip over or letting you walk around while playing, it lets you do more practical things like play the guitar as you hold it behind your head and spin around in place without needing to worry about a cord yanking your precious console from its perch. Plus, you can turn the Wii off from the guitar, take it off your neck, and be done with it. There's no need to take the Remote out to navigate the Wii Menu, either, because the guitar has an analog stick built into its body. It's just like a Wii Classic controller, only way cooler. (No, you can't play Virtual Console games with it. Boo!)
The cubby hole that houses the required Wii Remote includes an integrated connector plug that inserts into the Remote socket. The Remote slides in quite snugly into the guitar body, and there is even a space for you to keep the wrist strap out the way. The Remote doesn't move around at all while playing, and the hole cut into the face of the guitar body that allows access to the Remote face does not get in the way while picking at the strum bar. When I was really going at it, I completely forgot it was there.
There is only one drawback to the Remote cubby hole that I can think of. If you fancy those protective rubber sleeves that Nintendo has issued to prevent people from rendering others unconscious due to an errant Remote swing, I could see some hassle if you're constantly switching from the guitar to the glove with only one Wii Remote to go around. Of course, if you have more than one Remote you can just leave it in the guitar, or you can just ignore the rubber sleeve thing altogether.
So how about the rest of the guitar? On the plus side, the plastics used in the new guitar feel a lot more durable and stiffer than the previous Guitar Hero guitars. The fret buttons and strum bar work without fault. There's a new, additional strap anchor point behind the center of the neck near where it meets the guitar, which balances the guitar for left-handed players. The neatest trick of the guitar is it can break down into two pieces, the neck and the body, for storage purposes. When locked together, the two halves feel like one unit rather than two pieces that jostle around. In general, the guitar is very well-built.
There are a few issues, however. The biggest issue I have with the guitar is that the whammy bar feels somewhat loose and squishy, which is especially noticeable when trying to squeeze out some extra star power in the game. An equal annoyance is how the edge of the guitar can dig into your strumming-hand wrist when you're really strumming hard. The flat face of the guitar combined with the slightly increased thickness (to accommodate the Wii Remote) makes it somewhat boxier around the edge. My wrist naturally rests on such edge, and sometimes I had to reposition my arm to prevent the guitar from sawing my hand off. This was only a big issue for me on the hardcore expert songs with rapid strumming sequences, but I still found it quite annoying on the easier songs.
The reason for the flatter face and the more defined edges is because the guitar has a removable face plate. This is a nice feature because it allows for some creative customization. If you want to go further than slapping some of the included stickers all over the guitar (which is required by law), you can purchase a custom design. If you want to go even further, you can take the stock white plate and paint on your own creations without worrying about messing up the rest of the guitar. The customization aspect is brilliant, as it lets you take a plain production line guitar and turn it into your own. After all, shouldn't your guitar be your guitar?
Overall, you're going to like the guitar controller. If feels good to hold, and despite some issues, it'll feel fine while you're playing. But there's still the question of how long the controller will last. My personal experience with Guitar Hero guitar controllers in the past has been spotty. The controller I got with the original Guitar Hero bundle on the PlayStation 2 first lost its whammy bar, and then later, it fell apart completely. My friends have three GH controllers because the whammy bar and strum bar on one of them only works half the time. Even though the quality of the plastics and the construction in the new Les Paul has been improved from the PS2 models, I overheard at my local Best Buy store that they've been getting "a lot" of returns because of controller problems. It could be a local anomaly, and it could just be a problem with the initial batches. That's not the most encouraging of signs, though.
Still, looking at the big picture, you're getting a good, stable guitar controller with a fantastic game. It's not perfect, but it's plenty good enough to get the job done. Besides, it's the next best alternative to getting a real guitar, and you're not going to get a good guitar game with one of those.