I don't have an entirely positive experience with SEP. It's on a few thousand of the machines we manage. If I dial insight up it nags, and provides allow exclusions. The PUP/PUA detection in SEP seems a step behind Norton... and SEP seems more reliant on signatures then Norton..
SEP isn't anything like Norton.. from my experience. The technology in SEP Is heavily dependent on managed clients, but also the SEP technology is much more dated in some respects than (Norton), SEP doesn't have nearly as potent of a reputation engine, and it's insight features are quite dated.
The reason the development cycles on enterprise endpoints is so slow is because they can't break anything. Millions of dollars are at stake, and even a slight 'fracture' of something can cost a company thousands of dollars a minute. So basically EP products ARE using early 2000's technology in comparison to desktop.