I've had the M bars for a few months, just got the NH rearsets, and I must say they're a winning combination! The riding position really feels like a "boy racer", it's extreme compared to stock, but it works well. There is a lot less weight on your rear so the numb butt won't be an issue.
The M bars are mounted "upside down" so that they're lower, you can mount them either way.
The NH rearsets are great, a little pricey but worth it. Lucky for me I got mine used here in the classifieds. I was worried that the linkage would ruin the sweet shifting feel of the bonnie trans, but it did not at all. In fact, I think it shifts better than before! The brake side required a little more effort to install than the shifter side, but it was still a job that can be done in under an hour.
here's a pic:
Highly recommended!