Positive side:
1. We can buy without the use of mobile phone and cash in the future.
2. We can`t forgot to wear our watch because we always be reminded that our assets is stock on it.
3. It is not hassle because our watch has double purpose, it can be wear and it can be used to buy or pay.
Meh, first credit cards were marketed as "pay without your wallet", then both Bitcoin and banks were marketed as "pay without your card", now this watch is "pay without your phone". The next logical step is having a chip under your skin to always keep your money with yourself. Unless you're afraid someone will cut your hand off to grab it.
Negative side:
1. Vulnerable to snatchers or criminals, specially if your watch is branded.
2. If you lose your watch and private keys, goodbye bitcoin as well.
3. You can`t but to a merchant who does not accept crypto`s.
Hopefully the private keys are uncrypted and require a strong password. But I personally wouldn't trust a closed-sourced hardware to store my keys, who knows what security flaws it might have?
Also, this watch is obviously not a practical method for using Bitcoin, it's just swag. Bitcoin is supposed to be a money of the people, not some exclusive toy for billionaires, so we shouldn't care too much about things like this watch.