Thanks. I've evaluated Blue Iris as well and am impressed with the feature set, ease of use, and stability. The problem with it is the CPU load as you start throwing multi-megapixel cameras at it. It's currently stable for me with the direct-to-disk option enabled, the UI window minimized and two 3 MP cameras. This doesn't leave much room for adding additional cameras though. Another two cameras will be around 100% utilization on the quad-core i5 in my DVR machine.
I will give iSpy a look.