I've been using the proprietary nvidia driver for the X server for quite some time, but I wanted to give the free nv another try. One thing which immediately annoyed me was the smaller font sizes when using nv. I solved this by adding a
DisplaySize 370 300
directive to the Monitor section of my /etc/X11/xorg.conf configuration file. This basically tells X how big my monitor is in millimeters and X uses this to calculate an optimal font scale factor.