I must agree with Gruber, the updated MLB At-Bat is great because I can now get updates on all games with a quick glance without having to engage with my phone and I think we all know the stated reasons for times when engaging with your phone may not be appropriate or convenient.
You must have been reading my mind because I almost considered starting a thread asking why does the Watch need a so-called "killer app?" And my mind began to think back to 2007. I don't recall a killer app for iPhone. Even when the app store came about a year later, I don't recall any one app the masses generally found they couldn't do without other than as you allude to the phone harnessing the power of the Internet.
Now that I think about it, the way so many people on these forums complained about how the watch is "useless" without a paired phone, couldn't the same thing be said for iphone? How useful would it be if it weren't able to connect to the web in any way (WiFi or cellular)?
One could argue the killer app on the original iPhone was Safari. The killer "app" for the watch might be Siri.