- Certain letters including C, D, and S appear shorter than other letters, because of their round tops. Optical illusions cause letterforms with round edges (C, O, S) or pointed edges (A, V, W) to need to extend slightly farther in the rounded/pointed direction to appear to be the same size as other straighter shapes. This is called “overshoot” (https://en.wikipedia.org/wiki/Overshoot_%28typography%29).
- The spacing and kerning both need work. Letter pairs such as OV, FR, IA, AI, KE, EY, OX, MY, AP, and RT are too far apart. I’ve found that it’s easier to kern if you look at your outlines upside-down and backwards (I know Fontlab Studio has a built-in option to preview text in this manner, Glyphs might as well). Doing so helps your brain regard the outlines purely as shapes without getting sidetracked by their semiotic significance.
Another trick to type design is understanding that mathematical/geometric precision do not always result in the appearance of mathematical/geometric precision. Measurements that should theoretically be equal (such as the heights of letters as previously mentioned) often need to be fudged in order to look equal to the imperfect human eye.
The forums at Typophile are a great place to have your work critiqued by professional type designers (http://typophile.com/forum/1). Or, feel free to contact me if any of this is interesting and you want to know more. :)