Megacam was installed on October 2, 2009. Initial testing showed 0.6 arc second images FWHM. More photos are near the end of the "F/5 WFC and Megacam" Flickr set (click "Next" under the photo matrix).
Before installing Megacam, the F/5 secondary mirror was installed, along with the three sky baffle components, a new primary mirror center-hole protective shroud (needed for the baffles), and the F/5 wide field corrector.
This is a histogram of stellar image sizes in arc-seconds across a Megacam image:
That's 0.37 arc seconds typical across the 24 arc minute field of view.