The biggest issue it has is battery life.
From real-life experience, that's not been an issue at all. You just charge it at night when you go to sleep, or if you forget while you take a shower, and that is enough.
It has other issues, but battery life simply is not one of them.
Sure for fitness tracking it's good but there are better fitness trackers out there
Just like there are better cameras than an iPhone, but the iPhone takes more photos than any of them because the REAL better camera/fitness tracker is the one you have with you. I never, ever would have bought a fitness tracker, I didn't even want that from the Apple Watch at all, but I actually use that feature all the time because it's so well done - and it is there.
Whereas the Apple Watch is just more of a gimmick
I totally agree the Apple Watch is not a game-changer. I don't think everyone will want or need one.
However, there's no way it's a gimmick. It is quite useful already, and with just a bit of understanding of what apps can do with WatchOS 2, you can see a lot of third party power being brought to bear on how useful the device is - but even without them core features are compelling enough that there will be a substantial number of people who enjoy using the watch.
Customer satisfaction numbers for Apple Watch owners are even higher than the iPhone, higher still among non-technical users - THAT is a huge clue to anyone willing to think about the implications. A product with satisfaction numbers that high is not a gimmick, and will have staying power in the market because people will keep using them, and furthermore tell friends they enjoy using it.