Physics noobie thoughts

There's the sonic boom, when you cross the "sonic threshold". What happens if you stay at the speed of sound? Does the wave amplify and "throw" you out of it (and speed)? Do you ride the wave?

Same thought about ftl travel. What happens if you reach the speed of light? The image of everything behind you freezes, as you connect with the last photons faster than you, then everything there disappears, right? Behind you, everything is black, because no light reaches you from there any more.
But when you drop out of ftl, you get your image from the whole trip, pouring onto you, all that light catching finally up. Does it build up along the way, hitting you when you stop (supposing you get to full stop)? Optical overload, photon kick in the ass...?