I've only been playing cello a short while and one of the few things I didn't like about it was having to sit down while my bandmates bounced around.
Having the Shoulder strap is a revelation! It's very easy to attach to your NS cello and, once attached, it feels very secure. The slight change in playing position took a little getting used to, but only a little.
The one star this has lost is due to the fact that the actual strap part of the system seems oddly long for its purpose. Even with it at its shortest I could still do with the instrument being another inch or two higher when I'm stood up, but the buttons it attaches to look universal enough that I could use a shorter strap if it was a massive problem, which it isn't.
Overall I am loving being a mobile cellist!