In previous versions we did some aggressive memory trimming to try to keep the DisplayFusion working set as low as possible. This led to performance and stability issues. In Beta 4 we decided to try and run DF without the memory trimming enabled, just to see if we get improved stability from people reporting other issues. If we don't see any improvement we will revert to the old memory management techniques. However, if you'd like to force DisplayFusion to run as trimmed-down as possible, you can use this Advanced Setting:
http://www.displayfusion.com/AdvancedSettings/#general-memorytrimenabled

Because DisplayFusion is a .NET application, Task Manager will always show a very high memory number for the process. If your system ever gets tight on memory, DisplayFusion will trim itself down, there's no need to worry. The performance gains come from not having to do that when you have lots of free memory. If you have some free memory, let DisplayFusion use a little bit of it to speed itself up.

Thank you for being so understanding! We knew this change would generate a few concerned responses, but we felt the added performance and stability justified the extra memory.