What computer system are you using? Linotype's FontExplorer is (generally) well respected on the Mac OS side.

I'm using PC/Win

I'm on trial of font explorer, it seems like it lacks a lot of features that typeDNA has like harmony, find fonts according to weight, serif only etc etc.

Does it say anywhere how it determines things like serif vs. sans, etc.? Fonts have the capability to have that information in the Panose area. Unfortunately, in a large percentage of fonts the Panose information is, to say the least, weak.

- Herb

I'm not sure but it worked quite well. You can try it for 2 month(I think) and try it yourself. visit http://typedna.com/
As for the moment it gives me best experience. The font preview is sharp compared to others(to my eye). You can also access google webfont and activate the font directly. I tried FontXplorer and didnt like it, Still considering purchasing TypeDNA or not.

According to the FAQ, it determines serif, etc by an analysis of the glyphs, not Panose info...