given the reviews that are out, i guess that is not really true. the A5 was pretty fast back in the day, and can still stand on its own.... most people are saying the apple watch is too slow
It is true. For the most part, the Watch interface should be fluid and fast.
But, the way that the 3rd party Watch apps work right now is that if you click a user interface button on the watch, the watch has to send, via bluetooth, a notification to the iPhone that the button was clicked, the iPhone then runs that specific code, and then again, via bluetooth, tells the Watch what to display.
So the delay is purely with bluetooth. The current limitations of WatchKit is that no 3rd party Watch app can run code on the Watch itself.
So Apple apps feel fast and fluid, 3rd party ones, not so much. In time, this will get better as Apple allows native Watch apps to be developed, probably during WWDC this year.
The A5 is fast, and for a Watch, it's insanely fast. I imagine Apple underclocked it, but don't assume the Watch is slow because the way Apple limited the 3rd party apps.