I pretty much agree with most of the complaints here, most notably the speed and lack of good 3rd party app support. But one big pet peeve I have that I haven't seen listed here is this:
I use Siri dictation frequently. Or, I try to.Sometimes I get "Apple Watch failed to take dictation" and then if I try again right away, it zips along and captures what I said perfectly. But, every so often, I'll dictate a response and watch as it "types out" the words I just said. Everything looks good, so I hit Send. Then, suddenly, several of the words on screen start changing to different words, and then the text immediately sends. I don't know why it does this when it writes out the text perfectly, but only changes once I actually send it. Can't even count how many gibberish texts that I've sent to my confused friends.