As subject header... Many of the Matlab apps submitted to file exhange by users look very interesting and I'd love to try them, but I'm having no luck installing.
The documentation I can find only makes mention of apps (and the app tab) in 2012b, but I see comments on at least one app submission page indicating I can install in 2012a.
Can I install and use apps in my copy of 2012a, or am I out of luck until my college move to b?
It depends. Many of the apps don't depend on this latest release. For example, none of mine do since I developed and uploaded them when I had earlier releases. Even apps developed on R2012b might not require R2012b and might run fine on any number of prior versions. Download it and give it a try. I would say that the vast majority of apps in the File Exchange do not require R2012b.