I HATE that the Mac App store still doesn't let you download old versions of apps.
Things that downloaded fine on 10.6, 10.7, 10.8, etc now refuse to download/install, because they now "Require a newer version of OS X."
On of my MacBook Pro systems goes up to 10.7.
Some of our older systems (32-bit Core Duo) and ones required to run certain PowerPC apps can only go up to 10.6. I used Twitter on one to send outage notices, and it was updated and dropped 10.6 support a long time ago.
I can load old iWork '09 and iLife '11 apps from disc, but I cannot get much of the other software I use to be able to get.
Interesting. I was able to download old versions of iApps when I went back to Mountain Lion.