We've had a sebae now for almost 17 months and it really doesn't wander much at all, if any. Biggest move it ever made was pulling its foot out of the sand at the front of the tank and putting it in the rocks behind it. It seems to be a very laid back anemone, even when our goby got scared in a move and hid with the clowns, under the nem tentacles, it was fine. We did shoo it away though, didn't want to take any chances!
We've got anthelia, zoanthids, gsp, mushrooms, two toadstools (a small one for a friend) blastos, candy canes/trumpets, trachyphillia, hammer, and a few sps. We have MH on the tank too. There were some zoas growing near the nem, and they are closed up, but I don't know if it's so much from being stung or lack of light, the nem creates quite a bit of shade. What's happened though, is that the nem takes up about half of our tank (it's a 30 gal, some of the livestock will move to the 75 in a bit), so when we add things, we don't add on the side the nem is on. Over there we put up with the bare rock since the nem stops things from growing. So far this has worked for us, we just know not to put things with in the nems reach if we want to keep it.
HTH!