I used to [look at the Linux source code], for Plan 9. They were always ahead of us—they just had massively more resources to deal with hardware. So when we'd run across a piece of hardware, I'd look at the Linux drivers for it and write Plan 9 drivers for it. Now I have no reason to look at it. I run Linux. And I occasionally look at code, but rarely, so I can't really tell whether the quality has gotten better or not [since 1999]. But certainly the reliability has gotten better.

Ken Thompson; cited in Seibel, Peter (2009). Coders At Work. p. 479. - "Coders At Work", 2009