Sorry for my english in advance.
Impossible to deactivate updates: Updates have a lot of bugs, and Garmin spend very long time to solve. you spend your money to be a lab rat. You cannot decide by yourself whether you want to update or not.
Completely dependent of internet: Not possible to configure anything without internet, like alarm, appearance, widgets, etc, and these functions cannot be modified via watch. I really don't understand why!
Notifications apear when you are using cellphone: It make no sense because you are using your cellphone, no need to spend the battery notifying things you are viewing in your phone!
Same Icons for any notifications: Whatsapp, message, all use same white icons with same format (sometimes I think this watch not use a color LCD and have no pixels to create another format), and not possible to customize. Nothing is customizable because it uses a proprietary software source. I wish it become Open Source someday so that it can really deliver its full potential of this hardware, because the hardware construction of this watch is fantastic, but limited by software!
Now (3.90 update) it wake up with any vibrations: Any movement with the arm/wrist awakens the watch. Like wash your hands, ride a bike or motorcycle, clap hands, etc. The battery didn't last long, so now the watch lives in the socket charging. I bought a desk clock, I think.
The music commands is hard to access: If you are using your cellphone as musicplayer and watch as remote control, you need a lot of steps to access menu on your watch to change a music. So, is more fast and more convenient you take your cell from your pocket and change!
Gestures is very poor feeling: When you need to "click", the watch swipe for next menu or not understand your click. If you need a double click, even worse! If you swipe, the watch think you click and enter in options. It has a life of its own!
You may be asking yourself: why didn't he send these suggestions to Garmin?
Because as you can see here in the forum, The Garmin has not cared about customers!
I’m not remembering other annoyances right now. Can someone help me list others?