I am convinced one major possible flaw, probably the only one, is discontinuous curvature, like in this example:
 

A bad curve has bumps that stick out in like tumors in places they shouldn’t, usually because someone is using too many BCPs. Curves that do no smoothly transition to straight lines when they should can also be considered bad. This sort of stuff is often unnoticeable at text sizes, but in signage it can be pretty gross.

The easiest way to understand this is to open a font by Christian Schwarz or Hoefler & Frere-Jones and compare them with some of the crappier free fonts out there.

J.P. De Gregorio has a good article, scroll down.

Top: Bad Curve

Below: Good Curve

I’m missing the photographer here, but that’s a good curve,

less than good (although appropriate for the baked goods)

Thanks everyone.

Alessandro / Jupiterboy,
“:¬)

-=®=-

just an observation, but it’s interesting to read the opinion that pure curves are necessarily good. I feel that creating smooth curves in this way leaves me wandering what I am giving away, what I am letting myself being deceived into accepting as ’true’, precisely because they are clean. There’s a funny blandness to smooth bezier curves that inhibits drawing I feel. It takes a while to become confident enough to intentionally throw bumps into the mix. Or maybe that’s simply a case of understanding lettershapes better. I don’t think so. I spent several months painting letters with gouache, and when first drawing by computer, the technology naturally at first inhibited. In fact it did for a long time.

Blandness is a good thing with fonts. Normally fonts are a container of information, not a piece of art of themselves (I know this will be disputed by some). To condust their primary goal, of smoothly conveying information, they should not draw attention to themselves. (At least to the normal reader. A typographer will look at type in an altogether different way.)

A smooth curve is the most efficient curve. It’s harder to do, but looks more effortless.

I think this is more complicated than Tim indicates.

Getting smooth curves with the pathway and weight you want is indeed a key challenge in drawing with bezier curves. But less smooth curves, and even discontinuity are not necessarily design flaws. In the case of the Tim’s