Don't think of it as a replacement for your smartphone, think of it as an accompaniment. For example, in a meeting, if my phone vibrates I can't pull it out to see who's calling - if the call/SMS/email/whatever is important enough for me to excuse myself and attend to it. This majorly irritates me and a smartwatch which shows me who's calling or the contents of the text would be very useful.
Then, I ride my Suzuki GSX-R600 to work and around the city and use a bluetooth headset (worn under the helmet) while riding. Now I can't actually take calls with one unless I have autoanswer enabled and that is not something I like doing - I do it only if I am expecting an important call. If I could tap on my watch to take a call, that would be immensely useful.
I would happily pay $150-$250 for the functions I describe above.