I did NOT test this map multiplayer because im having problems with the internet, but i think i got a quite good view on the game from singleplayer.
I didn't find many problems singleplayer, but then again i didnt see many of the triggers in use. All powerup's tooltips say "press DOWN arrow key to use" whilst its the "S" key that actually triggers them. I assume you used the arrow keys before but forgot to change the tooltip.
Anyways, to fix johnfn's problem with circling around eachother trying to find a angle you could add a ability (either one you allways have or a buoy) called "throw the anchor" which would quickly slow the ship down alot to allow sharper turns for 2-3 seconds and then speed the ship up again.
Thats all i have to say, all in all a great map. Approved.