I think the insteon developer (jdecker iirc) has sort of disappeared... I, two years or so back, was torn between zwvae and insteon. I'm not sure what was the tipping point, but I went with zwave and never looked back. With a risk of sounding like I'm kissing ass- the zwave developer (Hari) has done a kick ass, top notch, job of integration. With a few minor issues with the zwave t-stat (eg no F or scheduling) the rest has been amazing and on top of that Hari has been very willing IMHO to integrate new devices for little more than gifting him a device...
You may see in other posts that for new buildings, KNX is the crem-della-creme, but in the States I've found installers had to find... FWIW I highly recommend zwave for the reliability, selection of devices and simplicity of integration into LMCE.