comparison between Helvetica and Helvetica Neue
I did more investigation on the rendering problems reported for Helvetica Neue (the preferred content font in VectorBeta). It turns out Helvetica Neue has serious problems with "combining characters" (http://en.wikipedia.org/wiki/Combining_character). The common ones are fine, like grave accent, acute accent, tilde, umlaut, etc. But as soon as you try the less common ones, the rendering goes to hell.
I don't know much about where these more obscure combining characters are used, but I know they are common in Vietnamese (which uses a modified Latin alphabet), and in the International Phonetic Alphabet (which is often used for pronunciation guides on en.wiki).
The attached screenshot shows a sample of the problem. The left-hand column shows the correct rendering in Helvetica and the right-hand column shows the incorrect rendering in Helvetica Neue. I haven't done an inventory of which characters display incorrectly, but most of the ones I tried randomly failed. There are about 200 combining characters total in Unicode.