Really interesting review and forum thread.
I'm sure you are aware that being 6'6" your mileage may vary from a lot of people regarding ride quality etc. I'm 6'3" myself.
That white text and grey background on your blog strains my 53 year old eyes btw.
Last summer I wanted a carbon bike after years of titanium and had narrowed my choices down to a Cannondale Synapse, Spesh Roubaix, or Giant Defy.
I also have a Moots VaMoots that is about 10 years old. I expect titanium to last longer and be able to take more knocks than any carbon bike so we differ some there.
The last carbon bike I owned previous to this was a Trek 2500 in 1988 when I was living in Hawaii. I thought maybe 2012 carbon bikes might be a little improved over the 2500...
The Synapse felt sluggish when accelerating and in handling and was ruled out right away. Not what I was looking for in a carbon bike.
The Specialized felt soft which I think is partly due to the wheels but I could also flex the bottom bracket on an SL 3 which really surprised me. In fact all the Specialized bikes I rode felt surprisingly unremarkable.
The Giant on the other hand had what i wanted and was expecting from a carbon frame. Very stiff but comfortable enough with great handling. One of the things I did not realize is that a stiffer bike is a better handling bike because there is no flex so you can tell right where the bike is going to go. I don't notice flex in the rear stays and the handling is pin sharp for me but maybe thats down to our 3" difference in height.
The Giant is point and go as you said about the Kyklos. Descending fast on winding descents is a blast on the Giant.
I expected I would use the Giant for short fast rides and the Moots for everything else but I mostly ride the Giant now on any sort of ride and love it. As you say Giant bikes are a great value which was not a primary concern but nice to save hundreds and still feel like I got a bike better than everything else I tried.
I will be testing the SL 4 Roubaix. i prefer the higher head tube and slightly more relaxed geometry over the Tarmac. The SL 4 Roubaix has a slightly shorter head tube and tightened up geometry from last year. If I like it I'll get one of those to add to my rides.
My brother has an older Tarmac and Roubaix, one with Dura Ace and one with SRAM Red and agrees with your description of the front end as twitchy. Doesn't care for the SRAM red though.
I also had Keo Blades but dumped them for Dura-Ace pedals because they looked like ass after not many miles. About 8 months ago I switched to Speedplay to see if they would alleviate knee pain from two surgeries on my left knee and found they did so I haven't looked back.
Why do you care about weight at 6'6"! The Moots isn't that far off and you need one!