It would be nice if upgrading in the future was just a matter of popping in replacement batteries and a software update. I hope the whole controller assembly wouldn't have to be replaced.
That's what I'm hoping for as well. Better yet would be an upgrade path with a higher capacity or lighter-weight battery pack from Brammo in 3-5 years. I'd love to see some more transparency, or at least a declaration of intent.
I'm looking at the Empulse from a couple of perspectives: as a commuter bike, and as a weekend rider.
My typical commute is about 24 miles at 35-55 mph, depending on afternoon activities it can be as long as 40 miles at 35-75 mph. I was more than a little uncomfortable with Brammo's 40 mile claim with the Enertia and its 3.1kwh battery pack; 60 miles from a 6.0kwh pack is a bit more realistic. The 6.0 would be adequate for most days; a higher capacity battery would give a bit of insurance for unexpected detours or degraded capacity over time.
I often ride weekends with a small group of friends: we'll ride 30-50 miles out and then back. Often one leg is highway, the other leg is back roads and twisty bits. Sometimes we stop to eat at our destination, and I could perhaps grab a kwh or two of charge from the proprieter. The 6.0 might make a shorter trip with a charge during a break; the 10.0 could probably handle a longer trip with a charge, or a shorter trip without recharging. In fairness, we often stop to refuel the gas bikes partway through the trip as well.
Overnight travel is also a mixed bag. Common overnight trips that I might take on the bike are 80, 120, and 180 miles one-way at 55-75 mph. The 10.0 is probably barely adequate for the shortest of the trips, depending on highway power requirements.
Since I have a gas bike and a car, it's not critical to have one vehicle that does everything. So maybe a 6.0 empulse as a commuter is the way to go, and hope for continued improvements in battery technology for the future.