About a month ago I started having problems with my work computer, a MacBook Pro. First the VPN stopped working. Then the keychain went haywire so I had to keep entering passwords for the same services over and over again. Finally I decided I had had enough and asked IT to wipe my machine give it a fresh install (after backing up of course). That was fine for a week and then my hard drive failed. Thankfully, because of the backup I had already done (seriously people, back up) I had all my files available and started from scratch again. I also had something else that proved extremely helpful: a list of everything I need on my machine.
When I started from scratch the first time I started a text file and as I installed software or settings added that to the document. I ended up with a fairly complete inventory of my Mac’s software beyond the stock install and then saved it as a gist. Referring to that document made setting up my machine much easier the second time around. Another key resource was 1Password with its storage of software licenses – much more handy than searching through email for serial numbers.
Of course what I need to install on a fresh machine may not match your needs. I highly recommend making a document like I did before you need it. Starting from scratch can be helpful in removing cruft from an old machine and doesn’t have to be that painful if you’re prepared.