I have been using SE 2011 for about a month now.
One thing I noticed yesterday was that if the SE project files (*.vpw, *. vpwhist, *.vtg, *.vpj) are read only, whenever I remove focus from SE (to use another application such as Firefox, Outlook, etc.) and then go back to SE, SE takes approximately 25% of my CPU (per the Windows Task Manager). This lasts for about 3 seconds, during which time I cannot do anything with SE. The previous version of SE would give a warning stating that the project files were not accessible.
The SE project files are set to read-only whenever I check them in to Perforce. This could be very frustrating for someone that has not figured this out.