I think there was very little doubt about gravitational waves, but it's still nice to finally have a confirmation. That should silence even the very last critics of Einstein. The guy was a genius, there's no denying it.
Curious to see what comes outta this. With some more sensors, we should be able to see even more stuff in space. Especially stuff that is blocked by the milky way. When the sensors are good enough, we could potentially get a pretty good picture from the centre of our galaxy or something!
No idea right now where this will lead in terms of practical use. But when quantum physics were discovered, nobody did know what to do with it either and now we have this neat little micro technology. Time Dilation made GPS possible. So who knows what can be done with gravitational waves. Exciting! =)