Flip side - had the Shift and the Centroid last year. Both bows had a bunch of vibration in the riser, and I didn't see any improvement when they went to the grooved riser. I ended up with X Factor wraps on the top and bottom of the riser to tame the buzz.
They shot great for about a year, then seems to wander out of tune at random times. For a bow with a retail of $1K, I was preety disappointed in the long term wear and stability.
I, too, loved the solid back wall, and the bows were dead on at first, took a nice doe with the Shift opening weekend. The cables and string flexing into the sight window was not an issue, and I think the paralell cam idea is solid. MAthews went to draw stops, so the idea must work for others.
Shoot everything you can before dropping the cash, if your local pro shop won't let you try one out, find another shop. Too much money in a bow, to not test drive a bit before making the buy.