The upside is that Emacs integrates better to the Gnome desktop and
that we can control Xft-settings. After all, if a user changes
hinting she probably wants it for all applications. As Emacs now uses
the DPI value from Xsettings instead of from the X server, fonst look
the same. This isn't the case now, Monospace-8 on Emacs and
gnome-terminal look quite different.
That's a very good change, yes.
The downside is that user might be surprised to see the size of their fonts
change as the DPI value is now different.
If it can fix the problem that the default font size is much too large
for all my screens (a 1600x1200 21" desktop, a 1400x1050 14" laptop,
and a 1024x600 10" netbook), then I'm all for it, and I know I wouldn't
be the only user to appreciate the change. See bug#4547 for example.