So having tried ML in a separate partition on my Macbook Pro. I decided to give it a whirl on Parallels 7. Actually its not bad but it does have some basic issues I have found. For example the App Photo Booth does not always display camera even though I see the Green LED light up next to the camera. Sound also comes and goes and Quicktime plays audio but no video. Its a bit sluggish even giving it 3GB RAM and if your also having trouble with the updates through the App Store or the system updates. Don't worry this is a issue with ML. I have to say the Parallels option for ML is OK if all your doing is seeing how ML is and playing with its features. I don't think its a good way to test out anything. Its very hard to determine if the issues are on Parallels side or Apple's.
This is mostly related to the fact that there's no 2D/3D acceleration support in Parallels Tools for OSX (Lion or Mountain Lion), primary reason for this lack of support is the fact Apple doesn't show access to the required APIs.
