It just arrived. It took a few minutes to attach once I'd figured out you don't need those rubber things on the sides
It just snaps into place quite cleanly and appears to be well made. It definitely gives the impression that your machine has much more protection with the case on than without. It feels much more rigid.
I disagree that it adds any discernible weight to the machine itself. Looks wise I quite like it apart from the incase logo stamped onto the top! The material is good and gives much more grip when handling the machine.
My screen tilts all the way back as it did before the case was attached. There is no 'click' or noticeable stiffness when opening or closing the notebook. No ports are covered and there is absolutely no overlapping for connections.
And YES it does fit in the Incase sleeve with the case attached although it is a bit of a struggle - I imagine it will stretch over time. Overall I think your very mobile with your machine, especially travelling long-haul, then this is a decent investment to protect from the stresses of travel. Although at 40.00 GBP it is rather expensive for essentially two sheets of plastic.
Hope this helps.