Per Fungo's message, I have posted an indepth review of my process. I have posted my comments in this (as well as freestyle's other thread in the notebook general area). I have not had a bad experience and I am very happy with my system. Don't get me wrong, I believe the PCT customers feel the same way.
I wanted the piece of mind as well, and it was well worth it.
As for the question on whether the system comes with a WinXP CD, the answer is yes. I can not talk for the 8790, however, my GX7 came with the WinXP Professional CD and a DVD with a ghost image of my system. I had to use that already (first night) as my boot screen customizations crashed the system. So I used the DVD and it placed it right back to the original state when I received it. Very nice.
I have to agree with fatal1ty44 that a lot of the Hypersonic buyers have disappeared shortly after. I have thought about that as well - the "I have my system now, what do I need the forum for" mode. However, I was very appreciative of those who were early 8790 buyers and even the 8890s before hand that I want to give help as well. I posted my review in the notebook general area as it didn't fit into other categories, and the link to it is Ratmyr's GX7 Review
Last, and certainly not least - FT's comment is the most important. Go for the one that you feel comfortable with. If you order a GX7 the whole time wanting a 8790, there could be a chance that you will never be happy with the GX7. And the first time you have a major problem, you will begin to doubt it. For the money you are about to invest - and we aint talking a couple hundred bucks - make sure it is what you want and be happy.
Feel free to ask me any other questions.