I had 2 apps with cache data:
1. the system app "Internet" = 444KB
2. a user app called "RedLaser" (for reading QR codes) = 45KB
I turned off phone, went into recovery, then "wipe cache partition", then reboot.
It did nothing! The two apps still had cache, and I just deleted them manually in Settings -> Manage Applications.
So what does the "wipe cache partition" do anyway?
Also, if a phone is unrooted, is there a way to clean the dalvik cache?