Kind of an older thread, but since I've recently obsessed over and acquired a 5.9, and currently work at a Trek dealer, I thought I would add some stuff.
Finny59, It's not live on their website, but it's in stock and ready to order from their warehouse. I've seen the picture on the dealer site and the FD has the tell-tale long arm design for the 11 spd.
As far as the Roubaix vs. Domane stuff, I think it comes down to a different approach to reducing vibrations, specifically speaking of which frequency of vibrations you want to try and absorb. The zertz inserts are very good at high frequency road buzz type frequencies. The iso speed decoupler is targeting low frequency vibrations specific to very rough surfaces. It was very much engineered to the abuse of the cobbles. It's very, very good at it and reviewers typically note how the front end feels harsh in comparison. But that is mostly due to the fact that without a true pivot point, you're not going to equal the rear end feel of the Domane to the front end. They do have the asymmetric steerer and swept fork, but that can only do so much. To cut high frequency vibrations, they do use the iso speed bars with the foam pads, but I read elsewhere that if you wrap your bars really tight, you basically kill any advantage the pads would have offered. My approach: carbon bars, with pads with moderately tight tape.
Regarding the seatpost issue: I'm not going to lie, I am not too into the idea of being locked into a proprietary seatpost, or seat cap as Trek likes to call it. However, I have a setup where I carry the bike in the back of my hatchback with a fork mount. It requires removal of the seatpost, and having a nicely marked seattube where I don't even have to think about where to put the saddle height (and without an annoying piece of electrical tape) and a handy included 4mm torque limited hand tool, it actually works out great for me.
We also sell Cannondale at my shop, so I had thought about the Synapse. They went from one annoying seatpost design to a slightly less annoying one. We were happy when we found out they were going to a standard round seatpost, but that was before we got them in the shop and saw it was a 25.4 post that no one else was going to make (outside of BMX stuff) and a "hidden" bolt (because people who are shopping for endurance bikes are REALLY concerned about aerodynamics) that is nearly impossible to get to unless you go to the back of the shop and pull out the torque wrench with the right bit, extension, etc. Not a massive problem as it's usually a set and forget sort of thing, but it's a huge pain for setting people up on test rides and for my admittedly odd situation where I'm frequently removing the seatpost.
On the Sora bike: Man, I don't know. Our price on the non-disc 105 is $2,099, so I can only assume there is some sort of extra expense for the disc version. Maybe the result of a smaller run of frames for a single mold? Heck if I know. I wouldn't have done it. I would have just put the 105 on there and said "Yeah, the disc option is extra." But that's not my job.
And on the subject of matte black bikes: Man, I really, really did not want to get an all black bike. I had the feeling that it would just look immediately dated and so "vanilla" and something that ten years down the line, people would look at and say, "Oh, you must have bought that between about 2000 and 2015." But just like everything else bicycle related, I always want something colorful, go back and forth, never can find one I really, really like and end up with something in all black. Whatevs. It looks amazing. (5.9 DA)