I've been running Probe For EPMA and Probe Image on my 2011 Macbook Air for 3 years using Parallels versions 6, 7, 8, and 9. I've also upgraded to Mac system to OS 10.9 Mavericks over time, but I've never changed the Windows system, which is Windows 7 64-bit. I'm normally operating in Parallels "coherence" mode, where Windows windows appear on the Mac desktop and not a separate Windows desktop.
I use PFE/PI like this all the time for data processing, training in demo mode, and creating software documentation. I have done workshop presentations with my laptop connected to projectors in seminar rooms/lecture theatres where I switch between Powerpoint running on the Mac side and PFE running on the Windows side. For the latter I vaguely remember having window size issues once but I've forgotten the details.
When I set it up the first time 3 years ago I had some aspect ratio issues in images in PI, but that turned out to be dodgy data files and not a problem in PI. Brian (Gaynor) is using a similar set up and helped me sort it out.
I can't say that I notice Parallels slowing down the Mac side. PFE does run a little bit slower than on a dedicated desktop PC, especially if the data files are located on a remote drive.
I'm very happy with the setup. I can work with the software wherever I am.
I second Anette's comment that using TeamViewer for remote control of a PC with PFE/PI also works well. I also use VNC. For VNC I normally just use the Mac OS built in "Screen Sharing" application. But you need a network connection.
Cheers,
Karsten