I've just done a fresh install of 15.10. After installing the nvidia drivers for my quadro 600, I was able to improve the tty resolution by setting:
in /etc/default/grub, but now when the password login screen displays, I'm unable to enter the password in the input box. I've tried ctl+alt+f1 and other things to try to enter it, but haven't found what works.
I'm able to enter it if I set nomodeset, but that puts me back at a low resolution.