I'm reading good things about the 28mm f/1.8 AFS on other forums. It's gets a lot of critical evaluation because there is stuff written about focus shift on the lens. But in practical landscape, PJ and event stuff, I've yet to be convinced that is is a problem that is readily evident in images. I haven't sprung for one because I have a 28mm f/2 AIS and it delivers regularly for me, plus it just doesn't flare so I find it great for night street and travel night-markets where I want to get close in situations where the lighting is often just a bare bulb.
Anyway, lots of choices. Review you images and see what you use regularly and keep notes on images-lost because of wrong focal length. Those too pieces of data will often help you define your requirement when it's time to expand.
Roger It's still, ISO, aperture and shutter-speed, right?