I upgraded from 12.10 to 13.04, and am having graphics bugs. Either the screen is blank with random colored pixels at the top of the screen or I get repeated patterns or colors.
I reinstalled (clean) 12.10, and then upgraded to 13.04 right after install. Same issues.
I did install intel graphics drivers from Intel's driver installation package on my original 12.10 install.
Setup : Intel Pentium G2020 (Ivy Bridge), Biostar H61 ITX motherboard