As someone who gamed on Linux in 2005, I can tell you that the experience was generally garbage back then.

I still remember making a bug report about the then ATI driver - performance tanked in certain situations in ut2k4, a game with a native Linux build. After months, they released a "fixed" driver which disabled some feature - so the game looked worse but didn't lag.

Then I was trying to get Enemy Territory (and its total conversion TC:E) - another native Linux game - to play nice. I ended up running a second X server so that I could alt tab, but that made sound even more interesting than it already was back then; a friend actually shipped me a PCI sound card to be able to use teamspeak in Linux.

Then came source games, which worked but were choppy and missing some graphical niceties. Then I gave up, bought a laptop so I didn't have to dual boot my pc, and never looked back.