I tried one and hated it. The connection between teeth and mouth is in my opinion much too solid. On very long dives, I find that in and of itself to be uncomfortable.
Unless you truly have an issue where you bite down way too hard on the mouthpiece, I don;t see the need for one - and even then, it makes more sense to focus on the problem - tension, rather than go with a moulded moutpiece.
In most cases, I think it is a lot more useful to focus on proper hose lenght and reduce jaw tatigue by reducing the hose imposed strain on the reg and jaws. That along with a reasonably well designed mouthiece will do a lot to prevent jaw fatigue.
From a reg tech standpoint, a sea cure mouthpiece makes many of the standard reg checks difficult to do with the mouthpiece in place, and they are very difficult to remove and reinstall. The potential result is if you have a busy tech and a sea cure mouthpiece, the reg may not get the same level of bench testing as one with a conventional mouthpiece. To ensure that does not happen you may want to remove your sea cure mouthpiece yourself befroe you send the reg in for service.