I have 3 QS8's mounted with the speaker wire connected to the mounting bracket. It takes a bit of work and patience to get a good connection where all of the speaker wire is inside the clamp. That's one design I'd like to see improved somehow. With a single strand wire, it wouldn't be an issue. But, with the 12 gauge multi stand wire, it can be a bit of a challenge.
Slightly longer screws might help, because now when you unscrew them to make the gap to put the wire in, sometimes the screws come all the way out, then you have to take the time to re-insert the screw. (This can cause some expletives to escape your upper orifice, if your're not careful.)
I talked to Ian about the power brackets when I visited last year. I have QS4s and on-wall M3s, not sure if QS8s are different. I found that i was trying to tighten the clamp on a very short (1/4 inch or less) section of multistrand wire (14 gauge, I think) and the wire slipped out as I tightened - several times and yes, expletives followed. I ended up drilling a deeper recess in the bracket to allow a good 1/2 inch of stripped wire under the clamp. Much easier! I have no concerns about the quality of the connection.