Preheat oven to 400 degrees, with racks in center and lower positions. Divide sweet potatoes between 2 rimmed baking sheets. Drizzle with oil, toss, and spread them in a single layer on sheets. Bake, flipping once, until centers are soft and edges are crisp, 22 to 25 minutes. Sprinkle with salt, and serve with lime wedges.
I've read where people blanch the sweet potatoes to help get them crispy (http://chowhound.chow.com/topics/378235). You also might try cutting them with a mandolin to get them a bit more thin. I LOVE sweet potatoes
I found these to be rather delicious - I love sweet potatoes in any form! Mine didn't get particularly crisp, but I've stopped expecting that of sweet potatoes. They were a wonderful accompaniment to a turkey burger!