I agree. I found Blue Iris in November 2011 (2.x) and at that moment I was sold. At the time I could not even imagine how much Ken could develop this awesome software and add excellent features what we have these days.
100% agree! There's room to make it even better like improving shadow cancellation and separate sensitivities per zone, and so on. But I couldn't live without it! I think I use it more than my smartphone.
If you update to the latest version of BI there is now multiple motion detection regions that are available to be used for things like line crossing. Still getting some of the kinks worked out, but it is there.