I'll start with the drawbacks. For the REALLY minor stuff, only power chords can be played, there's no way of palm muting or playing anything other than a sustained note, and you're limited to one octave. That's not a big deal for what's essentially just a toy and not exactly meant to be a replacement for a real instrument. In fact, I wouldn't have taken off a single star if it was just those issues. There are two slightly more annoying drawbacks that cost it a star though. 1. The responsiveness isn't great. the "frets" don't respond that well and there are times when strumming was iffy as well (rarely not registering a strum, but sometimes registering two when I only strummed once). 2. Washing can make for an annoying time. The neck and the amp are removeable fairly easily so you only wash the tshirt itself, but the cord for the amp runs through this cloth tube on the inside of the shirt that's a real pain to feed it through. Now that I think about it, I don't see why they couldn't have had just a little hole in the shirt where the amp wire meets the guitar-neck wire, rather than having to feed it through that tube. This CAN be avoided by simply plugging the amp into the neck and just leaving the cord hanging out, but then you risk the wire getting caught on something.
Onto the good. The tiny little amp can actually pack some serious punch (it goes to 11, so naturally Nigel Tufnel would be proud). There's a tone knob too, but it's very limited. If the amp that comes with it just isn't rockin enough for you, easily the best feature is the output. Most people will probably just end up using this as a headphone jack, but if you have an actual electric guitar amp you can actually plug it in using a 1/8"-1/8" cable with a 1/8"-1/4" adapter. I know, if you have an amp, then you probably have a guitar already, so what's the point of this shirt? Plain and simple, it's fun, regardless of whether or not you own a guitar. Besides, there's just something magical about running this t-shirt through a 100 watt half-stack and actually using effects with it.
Overall, I feel it's worth the price and is a lot of fun. You've got to take it for what it is though, a REALLY fun toy, which you just happen to be able to wear. You might not be able to whip out sick solos, or even mildly intricate lead lines, but believe me, everyone will get a kick out of watching you bust out the main riffs to Smoke On the Water and Enter Sandman on your shirt.