what richard said... don't judge battery life for a week or so.
between the battery needing a bit of "exercise" to get it up and fully running, extra "play with the new toy" time, and the watch also might be taking care of house keeping in the background.
Cellular shouldn't matter, the Cell radio only turns on when it can't find your phone, or a known wi-fi network. So as long as you have either of those, the cell radio is drawing very little to no battery.