As I said above, I upgraded to the 11 speed transmission (as opposed to the standard 9 speed). I'm not sure if the extra two gears are on the shorter side or the taller side, but I'm glad I got them. I like to be able to go up really steep inclines, so if I can get a shorter gear, then hopefully that places less strain on the chain (and easier to peddle-assist).
When I was on bike trails and bike paths, I was probably only going 10-15 mph, in the middle gears, since it wasn't the right place to break any speed records. When I got out by myself on a flat stretch of paved road, in the tallest gear, and pedaling pretty hard, it seemed to top out around 25 mph, without any throttle. If I applied throttle on flat pavement, in the tallest gear, it is capable of exceeding 30 mph. On a very slight decline, it got up to 34 mph. I only did this where I was by myself on a paved bike lane directly adjacent to a road with a 60 mph speed limit--when cars are going by you that fast, it actually felt a little safer to go faster.
The one thing I'm realizing is that all of the cool mountain bike trails near my house do not allow ebikes. After using the ebike, I'm certain these are the stupidest rules that have been ill-conceived by people who are not thinking it through, and mountain bike purists that want to prevent more people from enjoying "their" trails. While the bike is obviously capable of going very fast in the right conditions (paved road, level ground, straight shot), there's no way you would ever do that on a mountain bike trail. In most cases, the guys with the super lightweight standard mountain bikes are going WAY faster downhill than I could ever manage on this heavy bike. And going uphill, maybe they are going 3 mph, and since I have electric assist, I might be able to go 5 mph (despite my lack of spandex shorts). So if I want to get off-road much, I'm going to have to pick times when it's not crowded and just flaunt the rules, risking a fine. Or be confined to the road. Oh well...