Just cuz it is f/1.8 doesn't mean you should always shoot at f/1.8, lol. Try some similar shots at f/5.6 to f/8 and see how sharp that lens can be. The best part of fast glass is it's usually much sharper than slower glass at the same f/#. So your 50mm f/1.8 shooting at f/5.6 will be *much* sharper than my kit lens at the same aperture.
I just got my 50mm f/2 in yesterday, but I have to wait for the adapter to get here from Hong Kong (10-14 days, ugh!). I can't wait to try it out. I'm envious.