David Smith regarding the potential inconsistencies with the Watch’s activity tracking:

The activity tracking gets really confused by walking while pushing a stroller (something I do a lot). It counted roughly 40% less steps than my iPhone in my pocket for a long walk we did on Saturday. Certainly understandable since my wrist isn’t moving much while holding onto the stroller but frustrating nevertheless. I wish it would have more intelligently combined the data from my iPhone with the Watch to get a more holistically accurate picture.

He also notes something interesting about the heartbeats that are sent to other Apple Watch users with Digital Touch:

Also, it is worth noting that the heartbeat you send with that communication feature isn’t your real-time heartbeat. Based on what I can gather it looks to be based on the last measured value the Watch has. This is typically within a few minutes but still feels slightly less ‘intimate’.

This isn’t what I expected given Apple’s marketing of the heartbeat sending feature, but I hope this is something they plan on revisiting in future software updates.