I have all my hacks documented in a file. It's in the forum of "Filename/hack".
I changed this practise for my upgrade to 7.2
This documenting thing is fun in theory, but if you are as messy as me, you kinda forget things.
Using BeyondCompare, I compared my current install with 7.1.1 out of the box, re-applying hacks that I wanted in the to be uploaded 7.2 code.
My upgrade never went as smooth as this time. I was done in less then an hour, including backups before and after.