I'm sorry if it's off-topic but did the laptop hold up well? Did you have any special cooling mechanism?
A few years back cough I upgraded gcc from 3 to 4 and emerged system and then world. That was over 1200 packages. It took about a week. That was in the days when I used a Windows wifi driver and some unholy magic to get a connection. I parked the laptop on a table with the lid open and two metal rods lifting it up 6" for airflow. I left the nearby window open a bit too.
(I have to admit I stopped using Gentoo mostly because it encouraged me to endlessly fiddle with my system, and it would invariably end up broken somehow. That's entirely my fault, and not Gentoo's. I switched to Archlinux as my distribution of choice, and I manage to hold myself back enough not to destroy my installation.)
Beyond that the big win over performance even is customization. The most secure code, and the fastest code, is the code that isn't there at all. Do you really need your entire system to support LDAP authentication? Maybe... What about your local email daemon? Do you need that? Because cron does and since your mail daemon also has MySQL support built in, installing cron gets you the MySQL libraries.
I don't use it anymore because of the overhead, but there are a lot of performance and security benefits to be had there.
> Realistically, though, most software that can benefit from specialized instructions already detects their availability at runtime and uses those, even if the code was compiled with -march=x86-64.