This was my first road bike. I'm 5'6" and got the 51 cm version after going after measurements on competitivecyclist (which backcountry owns). Not having had a road bike before, I'm not sure if the fit is "perfect," but certainly after 30 mile rides I've been comfortable.
The 105 component set is great for the on-sale price of the bike -- hard to beat. Saddle is rather comfortable (though I'm rather light, so I'm not sure how heavier riders will find it).
Bike shipped from competitivecyclist and was mostly assembled when it arrived: all I needed to put together was to mount the handlebars to the stem, install pedals, put the wheels on (they're quick-release... no issues), and install the seat. A minor adjustment to center the brakes to the rims and I was good to go. Box was sturdy and the bike arrived completely intact.
The BC site doesn't mention that the chainring is a compact -- it's 34 and 50 teeth. If you need a third chainring, this might not be right for you.
I haven't ridden enough road bikes to be able to comment on stiffness or other subjective measures of a frame, but I've really enjoyed the SR01 and think it's a great bike with a great featureset for the price.