I'd like to see integration with HealthVault or Bing Health or really anything else so I can dig into the data a bit more. The Band icon in the upper right is confusing to me as band management - it should be a big tile at the top or bottom of the main purple tile stack that says "Manage Band". As you said, historical data should be easier to access by swiping. Pinch/zoom would be great, as would landscape mode for the charts. I'd love a battery diagnostics section to tell me what's eating the most battery on both the phone and the Band. I'd also love an app on the Band that has a tiny radar on it that shows me the location of my phone, or at least makes the phone generate a sound so I can easily find it.
Why is this not a universal app? I'd love to see the data larger on my laptop or Lumia 2520 tablet. I get that the sync and management would not work, but if the data is all in the cloud, a Win8 version could certainly view it.