I have the Neo Hybrid from Spigen, and while it does add some bulk, there's things about it that I have missed when attempting to switch.  The biggest being how incredible the buttons are.  I bought the official Google bumper case and the buttons are a complete joke with zero improvement after a month and a half of usage.  I went back to the Neo Hybrid and the button feedback is by far the best i've ever had with a phone case.  Again, it does add some bulk but I think it actually improves the look of an otherwise pretty basic phone design. 
If anyone is contemplating the Neo Hybrid, I highly recommend it.  Bulk is almost always a direct correlation to how much protection the case provides.  I'll take a tiny fraction of bulk if it protects better, which ultimately is why i'm buying a case to begin with.  But I also refuse to use a case that turns the thing into a brick.