I just got the Carrot Weather app and it's quite refreshing. It is grumpy, snarky and funny which is more than I can say for any of my other apps. If any of those have personality it's the anodyne Innocent Smoothie bottle persona, y'know - all cute and hand knitted mini hats. It addresses me as "meat bag" and threatens me if I touch its buttons. Alas, it doesn't seem to be entirely accurate, which coupled with its penchant for spurious accuracy, might get annoying. "Yay! Rain starting in 4 minutes" it drawls to an empty blue sky. It spent yesterday cracking jokes about non-existent fog. It breaks a fair number of UI guidelines about how to treat users, which is fine by me. My intuition is that if it gets too rude and starts buzzing my watch app, it will get dumped pretty quickly though. My sense is that the watch is a far more intimate interface and I seem to object heartily to intrusions on it (for example sales calls), more so than on the bigger devices.
And notice, any student of mine who might be studying embodied conversational agents, it is invisible. Yup, just voice.