Pebble's problem is the lack of features, and specific to users of iOS like myself, relative instability and weirdness when it comes to important things like notifications. The monochrome screen is also less attractive though IMO bearable.
Apple Watch's problem is battery life. It's absolutely unattractive to me to have yet another thing I need to charge once a day. It wins on pretty much everything else but such a low battery life is crippling to this sort of device.
I feel like between the two you have a rough approximation of the laptop offerings of the early 80's. Yes, they did exist and some people used them, but by and large they were terrible for the functions they were built for. I have a feeling in not even that much time, we'll have proper smart watches with good integration across platforms that will have a screen like Apple's and the life of a Pebble, but for now, laying out $250 for what's basically a bleeding edge prototype is unattractive to the mainstream consumer.
Edit: Question for HN: Would you all consider a Fitbit to be a smartwatch? I mean it's a watch-esque device that does more intelligent things than just a regular watch but I feel like that's more of a wearable monitoring device.