Since we're all web developers constantly tweaking and refreshing our pages/css a feature to disable the cache would be great.  I just wasted half an hour chasing a bug, I shift-refreshed a few times so I assumed that I was working on the latest copy.  Unfortunately it wasn't until I closed IETester and started it again that the cache refreshed and the bug disappeared!

Actually - since nobody uses IE tester for general web browsing, does it not make sense to disable the cache completely?