I'll make a plug for the Propel as I have been using it for road racing the last season. I have the mech Ultegra Advanced Pro. The ISP frame is probably a little lighter and not that much more expensive - I didn't get it due to the lead time at the time. Anyways, really excellent bike, brakes are great, monstrously stiff front end makes for great handling. All the Giant brand OEM parts are top notch. The bars may give you trouble - only Giant brand clip ons will work. They are really nice bars but the shape didn't work for me so I ended up switching them out.
There is a little bit of a learning curve to wrenching on this bike and fishing cables through. If I had to do it again I would have gotten the Di2. The 6800 group is really, really, really excellent, but between frame bends and internally routed bars you need to use the polymer coated cables and take some care with your housings to get it dialed. Once it's set up, no problems, although the front shift action will never be as smooth as on a 'normal' road bike due to the routing. Di2 mitigates a lot of these issues. I elected to not do it since it was about an extra $1k at the time. Then I found out that upgrading after the fact cost even more. If you are going to ever go Di2 in your lifetime, do it when you buy the bike.
There is a little bit of a learning curve to wrenching on this bike and fishing cables through. If I had to do it again I would have gotten the Di2. The 6800 group is really, really, really excellent, but between frame bends and internally routed bars you need to use the polymer coated cables and take some care with your housings to get it dialed. Once it's set up, no problems, although the front shift action will never be as smooth as on a 'normal' road bike due to the routing. Di2 mitigates a lot of these issues. I elected to not do it since it was about an extra $1k at the time. Then I found out that upgrading after the fact cost even more. If you are going to ever go Di2 in your lifetime, do it when you buy the bike.