Mavericks not switching to discrete graphics

This sounds like a positive development. Under 10.8.5 a lot of apps that did not require the discrete graphics card used to trigger its use. For example VLC used to trigger the discrete card by just opening the app (something that was not required), under Mavericks it does not. Most likely, Mavericks probably has a more advanced algorithm which determines weather to trigger the card or not, in order to maximize battery life. Parallels is a tricky scenario due to gaming. Most likely it can be fixed by an Parallels update or a setting in the Parallels preferences which automatically triggers the discrete card when the VM is launched.