You can check out the full list of discoveries here, but one big thing that stood out is that the next Apple Watch (or at least one version of it) will finally have LTE cell service, meaning it doesn't need to be tethered to your phone at all times. The leaked screenshot above shows a LTE signal strength indicator in the top left corner of the watch.
The benefits of a cell connection are clear - you could stream music or take a phone call on a run without needing to keep your phone in your pocket.
Interestingly, 9to5Mac says that your LTE Apple Watch will share the same phone number as your existing iPhone. This means that you'll be able to take calls on either device, and that plans may be less expensive than traditional data-only devices like an iPad.Traditionally carriers assign new phone numbers to devices even if they are only being used for data, like an iPad - so this is a new arrangement for carriers.
Lastly, a leaked setup screen from 9to5Mac suggests that the new LTE watch will have a red crown, to differentiate it from the older versions.
Two years ago, when the original Apple Watch launched, Tim Cook was spotted in an Apple Store sporting a version with a red crown. It's not clear if this means Cook was testing a version of the LTE watch in the wild, or the red dot meant something different at the time.