Okay I have now hit with the Q5 315. I have been using the Ki5 lately and it was interesting hitting both together. I have never found the Ki5 to be pingy, having said that, I found the Q5 to be a little more crisp and solid. I have been able to aggressively hit the ball in with the Ki5 and it continued with the Q5. The flex is noticeably different, the Ki5 is indeed more flexy and the Q5 is definitely stiffer. I think the plow is more with the Q5 and I felt I could drive my 1hbh quite well with it. I could really hit my approaches well with the Q5 and drive bh slices with good pace. Volleying was good, I don't feel that these 5 series racquets have awesome feel, but I can volley pretty well with both. I did not get a chance to serve. I only hit for 45 minutes(it gets dark early now).
I pretty much agree with Skeeter's assessment, a good thwacking stick.