If a non-retina app has issues on the rMBP goto it's info pane and check Open in Low Resolution. Not all apps have the checkbox, but some do and it can help. I was trying Canon's Digital Photo Professional and was very disappointed with the results. Images at 100% zoom were showing artifacts (lines) when panning making it unusable. I then closed the program looked at it's info pane, and checked the Open in Low Resolution checkbox. Now it runs fine. Only downside is the text in the folder window looks somewhat softer. Until its updated for retina mode at least its useable.