I have the 135 and the 150. Can't really tell the difference in image quality. Somehow I do prefer the 135, great focal length. For their weight and price they are hard to beat. Not a lot of character or the last word in sharpness, but plenty of both. Wide open it is quite a decent portrait lens and for landscapes it is plenty sharp. It just isn't really special to me, but a light lens for that price is very handy to keep around.
I think now that a lens between 110 and 135mm could be my only landscape lens. The 90 is great to have and often used, but it feels a bit wide when I'm shooting. I often really like the results though after developing.
My sensible kit is going out with a 90, 150 and a 210. My lightweight hiking and scouting kit has only the 135. You can pick them up very cheap and just sell the ones you don't want.