I can't recall the last time I used 640x480. But I do remember that everthing looked really big on a 21-inch monitor
Come to think of it, 640x480 would be a good choice for testing UT2003 on mid-range and low-end cards.
As for multi-player Quake, nothing has come close to the rush I had back then. A local ISP (VisiNet) ran a server and I played there almost every day for two years! One weekend, about 20 of us got together for pizza and we had players ranging from 12 to 52 years old.
We eventually started a clan called Deadly Rage and I finally made it in Clan DMOS towards the end of my playing career. Those guys really kicked ass!