Pros:
- Use less gas/oil, which for me is important at the environmental and social level.
- Fun!
- Maybe this one is part of fun... but I get to experience the city I live in, and love in a much more personal way.
- I can postpone hitting the 200K mark in the old honda civic just a little longer.
- Fitness.
- Parking is way easier.
- It's fun tinkering with the bike, and buying new parts or changing parts, etc.

Cons:
- Dealing with sometimes dangerous drivers.
- Less trunk space