With all the good qualities of the 24mm f/1.8, this offers an even lower price and better distortion numbers. AF was slightly noisy, but a newer (untested) version fixes that.
Standout Spec: Price—less than $400 for an f/1.8.
Lens Test: 18-55mm f/3.5-5.6G VR AF-S DX Nikkor
Sigma 12–24mm f/4.5–5.6 EX DG HSM
Sigma 10–20mm f/4–5.6 EX DC HSM
SIGMA 24–70mm f/2.8 EX DG HSM
Sigma 10–20mm f/3.5 EX DC HSM
SIGMA 8–16MM F/4.5–5.6 DC HSM
Canon EOS Rebel XS
Canon EOS Rebel T2i