I have the 28mm f2.8, 24mm f2.8, 24mm f2, and 17mm f4.
The 28mm is good but I much prefer the 24mm focal length.
The 24mm f2.8 is wonderfully sharp and is not lacking anything other than speed over the f2.
The 17mm f4 I'm not impressed with but lenses this wide take skill to use properly. Hostly I just havent picked up the knak of shooting that wide yet. So my opinion is biased.