There are definite flaws in the device. I find buttons unnecessarily hard to tap for instance (they should offer more vertical space), and the face is so sensitive that it routinely triggers unwanted actions. It is really annoying to start something I want (like a timer) and notice some time later that I somehow accidentally stopped the timer by hitting my watch on something.
As far as 3rd parties, I have seen a general trend of apps gradually withdrawing their support for watchOS. There just aren’t that many useful things to do on a small surface. For apps suited to this (timers, reminders, etc.) it is fine.