Glad you liked it!
The speed changing is mostly a preference thing, it's sometimes handy to go fast for some parts of a stage then slow down to dodge intricate attacks.
Homing's a little tricky to balance, right now it's got the lowest DPS but since you don't have to aim that makes it a lot easier to use.
What screen resolution and OS are you using? You might be able to fix that by alt-entering and turing on v-sync before going into full screen.