Sneaking in combat is very strong, especially if you're the only one alive. Aside from the few that seem to naturally see through sneak, enemies will just stand in place if you're in sneak. Investing in sneak is only worth it, though, if you plan on investing in it very heavily. One or two points isn't going to make much of a difference in the width of sight cones. However, once you start getting above 4 you'll really start to notice the difference.