On the Mac, the font for Input/Output is Source Code Pro -- a distinct improvement over Courier, which had been present since version 1. On my computer, at least, the new fonts are very sharp.
The other fonts -- Arial and Gill Sans -- leave a lot to be desired. Gill Sans is OK for Titles, etc., but Arial is an ugly font for display text. However, I am sure that Arial is still being used because it is available for all platforms. I'd prefer Helvetica over Arial, but would prefer a serifed font such as Garamond (Times -- the cross platform variant) is just ugly. When I make my own stylesheets, I use Optima,which is quite elegant for both text and headings, but is not generally available on Windows or Linux.
I have suggested that Wolfram adopt Knuth's Computer Modern, which would have the additional advantage of making LaTex translation easier.
As for the icon -- on the Mac, at least, there has been a 'fashion' of making slab-style icons for most apps, so at least the new icon does not stand out as being old-fastened by current taste. Taste changes, though, and perhaps the pendulum will swing back.
