Gentoo's "compile everything" approach doesn't seem like such a bad proposition up front, but it really turns out to be the PITA. Since it's a rolling distro packages get updated often and if you haven't updated you're system in couple weeks and you happen to have couple of heavy packages installed (chromium, firefox, octave, openoffice, kernel) upgrading your system may take up to 10hrs on a average 2015 machine.

Similarly, compiling flexibility didn't prove like important feature for myself also. It allows you to slim down package installations or compile them with different optimization flags, but in most cases you don't gain much by using them:

- smaller package installation (by turning off features not commonly used) in the time where disk is cheap and OS is not the biggest consumer of the disk space

- have marginally improved performance if you know when it's safe to crank up compiler flags (better leave this decision to package maintainers)

- have debugger symbols built in - if you happen to ever need to do this, doing it for the binary package is not that difficult; you shouldn't have source distro just for this use-case

Gentoo deffinitely excels in providing you with concrete reasons to deepen your Linux knowledge if you have it as a distro on your main machine, which can be both pro and con.