I think he means stable rather than mainline? I run the stable kernel, which I build myself. There is still the occasional regression. About a year ago it had

I think he means stable rather than mainline? I run the stable kernel, which I build myself. There is still the occasional regression. About a year ago it had a regression in the Intel graphics driver which broke graphics for my Haswell chip. A patch was available but this wasn't merged for months. Luckily Gentoo makes it super easy to apply custom patches so I did. IMO if you want to run a stable or mainline kernel yourself you might as well build it yourself too.