The first question that I always want answered when learning of a new font is how much of Unicode it covers. It a question rarely answered by "We have made a new font." blurbs, though.
Yes, yes; it's aesthetically pleasing, satisfies some set of geometric rules that you say fonts should satisfy, and smells of fresh lemons or whatever. But I want to know what happens when I put a diacritic on that letter "a". Is my system going to fall back to a different font?
Given that there are WGL4 and Unicode variants of Arial, it is a particularly apposite unanswered question here.
It contains 475 glyphs in total, including 13 diacritics for the letter A. The set includes most Latin characters, but does not cover Greek or Cyrillic
That's well short of even WGL4, and must lack a fair whack somewhere else in addition to Greek and Cyrillic if it's only 475.