This is my personal taste, but I find the shape of flats to be a lot less versatile than that of heels. Translation: I like heels to be rounded toe, and find both peep toe and pointy toe flats to be really awkward. I've never seen a square toe flat, but I'm sure that wouldn't look too hot either. I also tend to shy away from kitten heels.
And it may just be the short girl complex, but I find that kitten heels, which look and sound like heels but give minimal lift, tend to spark the reaction of "she's wearing heels and is still that short?!"
But for any girl, short or tall, I think flats are a perfect choice for occasions like shopping trips, park visits, or honestly any normal day. You can never go wrong with a fabulous statement flat.

Chinese Laundry

BCBGeneration

Nanette Lepore

BCBGeneration

Elie Tahari

Be&D

Matiko

SM
Splurge Alert!

Marc by Marc Jacobs

Tory Burch (comes in many colors/prints)

Jimmy Choo