1. I found some apps in mlappinstall format at MATLAB File Exchange. I understand that this was introduced recently (2012b or 2013a). Is there a way to retrieve the equivalent apps for the earlier versions(say 2010b or 2011b) from these mlappinstall files?
2. Weren't m files that generate GUIs while being run sufficient? Why introduce a new format for applications and create chaos?
1) The app is not backward compatible. However, it's a glorified *.zip file that can be renamed and have the MATLAB files extracted.
2) Apps are completely self contained. When you build an app, it will do the dependency analysis for you, grab all necessary files, and store it. It also takes care of all the path issues making it easy to distribute etc. On top of both of these benefits, you can have version labelling, descriptions, icons, images etc with them..