OK. You came for tip you get tips. Firstly, DON'T BLINK. (or rather, don't close your eyes.)

Don't be afraid to hit the obstacles after they touch the inner hexagon.

If you have one, use an Xbox 360 controller.

Turn VSync off. It helps.

Try to ignore the clock, or better still, move your level up sounds somewhere else.

Only perfect practise makes perfect. Make sure you are comfortable in playing before starting.
(Does that make sense?)

Practise on hardest(est) mode for 20 minutes, then go on hard(er) mode, you'll find it goes really slowly.

Go into /Steam/SteamApps/common/Super Hexagon/data/sounds and move begin.ogg and gameover.ogg to get rid of the "begin" and "game over" sounds. (Only checked on Linux, Windows and OS X unknown, should be silimlar)

Get to know the patterns.

This calls off the tips, you should be a little better now.

Oh, and playing with headphones doesn't annoy the life outta your peers.