-Although it looks great, it doesn't look like a great watch, it just looks like a beautiful Apple product. The thing is, on this specific product, as opposed to all their other products, Apple is competing with an established design lineage that goes back for decades, and wristwatches have always been about good taste and good design, so the competition on the aesthetics front is not so easy for Apple as it was on their other products (meaning computer hardware/software makers suck tremendously in regards to design, but watchmakers are champions of it).
-Extending on previous reason: it's as if Apple decided to go the eyeglass route and take on Google. Easy, because Glass is downright ugly and too geeky. So Apple makes its own beautiful glass, which is still a little geeky, and then they have to compete with Ray-Ban, Gucci, Prada, wathever.
-Short battery life sucks for a wristwatch.
-People already have the functionality on the iPhone, and the iPhone is already pretty portable.
-Short battery life sucks a lot for a wristwatch, come to think of it.
edit: formatting.