I'm of the opinion that electric bicycles are quite awesome, having been commuting on one for about a year now (second ebike - first one was a cheap proof of concept I bought from someone and rode for 10 months, then built a good one based on what I had learned).
I'm doing ~10 miles round trip in the Seattle area (so basically solid hills). I can take a muscle-powered bike if I care to, but in the dark and traffic, having more speed and more lighting is quite nice. I'm doing it mostly because it's the least-miserable option I've found for commuting 5 miles through essentially stopped traffic (estimates of time home are frequently far longer than my ebike ride).
Several bits of advice if you're considering an ebike:
- Build it yourself (or have a bike shop do some of the tricky bits if you're not comfortable with them). You can get a far higher quality bike for a lot less than buying one, though you do lose some of the integration. The prebuilt units are nice, just about 2x the cost of a similar DIY bike.
- If you live in the flatlands, 250W or 500W is fine. For a hilly area, 750-1000W is nice.
- Don't bother with any battery packs that aren't lithium based. I'm a fan of LiFePO4 due to it's general safety and long cycle life (the pack doesn't degrade quickly with cycles).
- You can add a lot of lighting. If you're riding at night, do it.
If you already commute on bicycle, then there's really no advantage to an ebike unless you've injured yourself somehow.
If you're not already commuting on a bicycle, building an ebike is a great way to have a far longer range on a bicycle than muscle power, and you can always reduce your assist level.
Be aware that in many areas, ebikes are not legal to ride on paths/trails.