I've always loved Unreal Flash, and games like it.
The controls felt quite good, and the adrenaline added something new. I haven't unlocked all of the weapons yet, but there seems to be a healthy variety. The sounds were pretty good (Although I would've liked a resounding "Headshot!" for headshot kills and perhaps "Double Kill!!" etc. ).
However, here are a few suggestions. First, ammo. I understand the need for a 'pickup' key, because in other games of this category it was always frustrating to run into a shitty gun on accident and lose your favorite weapon. However, a. when one runs into the same gun they already have, they really shouldn't have to press 'pickup,' it should automatically add to their ammo count. Sure, it takes away a little technical skill from the game, but overall it should really just be automatic. Furthermore, there shouldn't be a max ammo count for your gun. I understand that these two changes might allow one to use one gun exclusively without much thought, but again, overall I believe it's worth it. Also, the default gun's infinite ammo was pretty much necessary, though it does encourage one to simply spray indefinitely till one finds another weapon. Perhaps it could reload every 30 shots, possess some sort of cool down mechanic, or maybe just slow you down if you fire while moving.
I'll probably try to beat it later, but so far, I also liked the map design, game mode variety, plot, and graphics. The AI was decent too (although on that one giant drill map with CTF, an earlyish level, the opponents would frequently grab my flag and then run around in circles instead of scoring, and sometimes the opponents would act downright stupid). Maybe the characters could have been a tiny bit bigger (headshots might be better off a bit easier than they currently are), but meh.
Overall, great game!