There are some comments about the Ki Q5 here:
I demo'd the Q5 and the Ki5 315 a few months ago (I play with a 7g).
My first observation was the Ki 315 demo (11.45 oz) didn't match the specs published by TW (11.8 oz). The Q5 was closer (11.75 oz vs 11.9 oz). Given this, I was a bit surprised at how stable the Ki 315 felt on hard groundies.
Second observation was the Q5 felt noticably stiffer. Although my sometimes tender elbow was able to manage it, the Ki 315 was just much more comfy.
Third observation was I didn't like how the Ki 315 volleyed. It just didn't have as much "punch" as my 7g. The Q5 was more to my liking in this department.
I would encourage you to demo anyways. There aren't a lot of Q5 reviews yet. Funny how these are all supposed to be 315's.