They are called Toric Lenses and they correct for astigmatism. I have a very slight case of astigmatism, so when I view the world through contacts, there's a reduction in clarity in comparison to my glasses, but these toric lenses adjusts for some of the angles of astigmatism, so it's not quite as crisp as viewing the world through glasses, but it's pretty darn close.
Wearing them seems to tire my eyes a bit more than the normal contacts, but since it'll be about a week or two before my glasses arrive I'll have ample time to test between the two.

I know I've said this before, but when I tried on a trial pair of Toric lenses (now I know what they're called) they really irritated my eyes. I switched back to normal lenses shortly afterwards and have been wearing normal lenses since then. I also have a slight case of astigmatism although there does not appear to be a discrepancy between my glasses, which I hardly wear, and my contact lenses. =)
Correction: Toric lenses