[lxdude]

There's absolutely nothing wrong with the 50mm you have. The f1.7 version is sharper at larger apertures but it isn't worth spending limited funds on changing, you can still take superb photos with the f2 version.

Well said.

As to wide angle zoom quality: I have the tiny 24-35mm/3.5, and it's sharp and resistant to flare. It does have more barrel distortion than the wide angle primes, though.