I had Zoneminder working well for a while, but it's kinda clunky and device discovery is hit and miss. The interface is light years behind BI, but if you're willing to take the time to get it configured, Zoneminder is actually pretty capable. Zoneminder could look much, much nicer if they took some time to tweak the CSS.
I bought a copy BI to see if it was any good, and after a couple of weeks I decided to use it instead of Zoneminder.