I think a maxi dress has got to be one of the most comfortable and flattering things to wear. You can quite literally squat, sit, run, jump and never have to worry about things riding up or exposing themselves. The silhouette gives off a long greek like column that compliments everyone.
The trickiest thing about pulling off a maxi dress is finding one that is the correct length. Inevitably, most women will need to have theirs hemmed. In order not to ruin the line of the dress, look for ones with a fairly straight skirt. If you try to shorten an a-line skirt, you may end up with one that is too wide where you cut it to.