Previous to the MoPho I had the Samsung Intercept. It was a bit thicker than the MoPhoQ is and it never felt too bad to me. One thing I will say the casing makes all the difference in the world with a slider or any kind of physical keyboard even more than thickness. My Intercept was very slick and that wasn't very good for typing.
That is one thing I'll be interested in is how the back feels. It looks textured which is good IMO for typing and holding in general. Other than typing, I don't really notice phone thickness but I am a gal who has a pretty little Coach cell phone case so that part doesn't get to me as much as my husband or others LOL