Huge Croc fan here! I've got 5 pairs and counting. I trekked in India in a pair and they were brilliant - no rubs, blisters or squeaks. They are great if they get wet as they (and your feet) dry out really quickly. No more soggy socks and sneakers!
They are an absolute god-send to your ankles, knees, hips etc.
Can't recommend them highly enough. The fake ones are no where near as good IMHO, they made my feet sweat, didn't give as much cushioning and the strap was very tough. Crocs might be quite a bit more expensive but there really is a difference.
It's a good job I've got an expandable suitcase for Florida! I won't have to worry about excess baggage though as they are so kight.
The sizes do vary depending on where they are manufactured. Generally, the ones from Boulder in Colorado are about 1/2 a size bigger than the others. I've got pairs from Boulder, Mexico, Romania and China and the Chinese are the smallest with the others somewhere in between. The Boulder ones are a little too big but are so comfy and none of them rub as they are all loose. Whatever size you normally take go for that in Crocs too and you should be ok. I take a size 7 andthe M7/W9 fit fine.