I have this same setup too, as of yesterday.
I agree that the receiver is great and locks on to many satellites with ease. I too, used to have the old Delorme as well. It was horrible. iGuidance however has been pretty weird. I searched through the restaurants and found a place that I love to go to, and didn't expect it to be in there. So I set it up to give me directions there, and I followed them. When I got there it had me taking a pointless U-Turn at the end, which is okay I guess... but when I pulled into the shopping center, the maps didn't even know the center existed. Immediately it told me to "Please find the nearest road." Didn't make much sense to me. How can it know that this place exists, but not even really know where it is? Just seems like lazy programming to me.
I would like to try other software and see which produces the best and most efficient directions, but with each piece of software having a ridiculous price tag, that's nearly impossible. I love the idea of GPS, and despite iGuidance being (in my opinion) about 80% perfect, I still absolutely love it, heh. I guess I'm just a sucker for neat technology.