I installed 32-bit Gentoo Linux on my computer in 2002, and kept running that same OS install without reinstalling (but with nightly updates) for over a decade. (It's morally the same computer even though I've incrementally upgraded every piece of it except the keyboard and floppy drive. Kind of like George Washington's axe.)
But I finally ran into a problem with KDE that I didn't have the patience to solve, and decided it was time for a reinstall anyway so I could use a 64-bit OS and run processes larger than 4 GB. I went with Kubuntu 12.04 rather than Gentoo this time, to avoid having to recompile the world.
Kubuntu installed fine and worked fine for a few weeks, then I needed to reboot to apply a kernel update. And when I rebooted, it didn't come back up.
So I booted from the install CD into rescue mode, and Googled for "ubuntu fix boot" or somesuch. Ran into the page for the Boot-Repair utility. It's not in base Ubuntu yet, so I had to install it from a ppa. Then I ran it, and it fixed my boot problem, and I rebooted and all was well.
Normally this kind of problem takes about half an hour of web searching and/or reading man pages then a magic incantation using fdisk. Having a mostly idiot-proof program do it for me was pretty nice. Recommended.