@Chestnut What does your house look like? My highest priority would be to match the style, roofline, overhangs, etc to the main house as best I could (unless you plan on changing that stuff in the near future). Whenever I see people build secondary structures that don't match, it doesn't matter how nice it is if it differs too much from their house. Just my 2 cents. Add a couple pics of your house if you can!
Dormers add complexity. They look amazeballs, as @Alan G showed us, though. If it were me, I'd be hard pressed to justify it, unless I were retired .....someday (sigh).