I'm a longtime user of Parallels Desktop to run Windows VM. I also use OSX Keyboard Maestro (KM) extensively. Briefly, P6 (but not P5) breaks the use of a particular KM macro in OSX programs such as Textedit, MS Word for OSX, and R for OSX. Details: Frequently I am using Microsoft Word under Windows (the OSX version has problems) and simultaneously the statistical program R under OSX (the Windows version has problems). Among many other uses it helps me in statistical analysis with R (under OSX), to step through code. I program "^R" to simulate Command-Return, ^E (end of line), and down-arrow. "Run selected code or current line, then step forward." Very simple but very convenient. When I upgraded from Parallels 5 to Parallels 6, it broke. When I run Parallels 6, as soon as I start the VM, the macro becomes useless. The down-arrow happens not once but a random number of times -- anywhere from 1 to 7. The down-arrow could be any other key stroke (at least I've tried a bunch). If a second keystroke is added to the macro, the two get repeated the same number N of times, N of the first one, then N of the second. But the phenomenon only happens if Command-Return is in the sequence. Adding various number of keystrokes before or after, the length of the result is random but for each length the result is always the same. This is not specific to R. R uses a textedit-like window. The phenomenon also happens the same way in OSX TextEdit or in MS Word for OSX. In these editors Command-Return doesn't normally do anything, so it's not a side-effect of its effect in the OSX program being used. As soon as Parallels quits, the KM macro is back to normal; the random-multiple keystrokes problem goes away. I downgraded from Para 6 back to 5, because this problem is worse than any benefit I've seen with 6. The problem goes away with P5. I'd sure appreciate any insights.
