This game is a lot like the tank game I was
developing in my free time, until having to work 2 jobs took all that.....
. Granted you got a lot further than I did. I felt it ran very smooth and I would give it an all around good score. I really enjoyed the speed of the game, which was my main goal in my game. I was aiming for an arcade feel, for the casual user to come and just blow stuff up. You captured that well...good job.
I have yet to try out the online play due to working places w/ very restrictive firewalls. The single player was fun until I was spawned right by the computer player and I couldn't get away let alone kill them....lol.
Have you profiled your server? What's the max numbers of players set to play in a game at a time? I would guess it's pretty small due to the size of the maps.
Overall this game has a lot of potential and if you need any help w/ development I would enjoy too.