I gave some thought about getting an electric bike for my wife for commuting to work. In our case it would be beneficial since a special license wasn't required and would be easy cheap transportation for her..
From your link, I'm assuming that you're planning to use it for off road back country travel. I like the idea of the trailer for hauling in your gear or packing out your game be it elk, deer or whatever. It claims to have a 60 mile range battery which would be about all you'd need for a day out. but I'm thinking carrying a spare fully charged battery pack as a backup safety precaution or else a means of charging. The fact that e-Bikes are so quiet would be a great asset also for approaching game or entering areas you plan to hunt. I don't think I'd go any slimmer then a 3" tire either as it will give you a better footprint for traction and avoid sinking into the ground..
From the description they give of this hunting e-bike that you linked, sounds like a great e-bike. With off-road e-Bikes ranging in price from $1500 to around $7000, they're cheaper then ATV's which start at about $3000 and could go up to $20000 or more plus ATV's are noisy..