I agree about dual-tech sensors... I have an outdoor Insteon single-tech (IR) motion detector and during the day it can be way too sensitive... i.e. glare from car windows passing by 50 feet away on super sunny days will register. It's decent at night, though. Dual tech should def. help with the day problem, but I don't rely on the sensor during the day, so I haven't found the energy to run a hard line out and replace it with a dual-tech sensor.
I haven't had any problems with my z-wave network having connectivity issues, though... but as with anything wireless, everyone's experience is going to be unique.