Unresponsive and not challenging at all
The weapons are unique, indeed, but they aren't fun, simply because some are useless and others are broken. The latter make the game pitifully easy even on one's first playthrough. There's little point in having fun trying out 21 weapons when only about four are worth a damn in combat. Also, holding down the mouse button to fire makes movement rather unresponsive, which makes fine adjustments for skillful dodging virtually impossible; instead, you just have to give all the shots a wide berth, which leads to circling lamely around the rather crappy AIs because -- as if the game weren't easy enough -- the player ship is agile enough to evade pretty much every enemy except one or two fast types with ridiculous ease.
I'd say it's fun for a short break when really bored, but that wouldn't unlock the better weapons, so it's not even good for that.