Parallax Scroll said:yes yes yes yes yes yes
Edit: A friend of mine went out and bought a gamepad specifically because he couldn't beat one of the bosses with a keyboard.
Update: I'm at the final boss tonight (I think) but I have to take a break for a while, my hands are killing me (I never play PC games, and I never got that gamepad, I've just used the keyboard). I have the Snake, the Bubble Blaster, the Rocket Launcher, and the Sword, I read somewhere earlier in the thread about skipping the machine gun, which I did, for better or worse.
A couple of questions: I found a little blue mushroom-looking guy in a cave who said I didn't need his help/he couldn't help me, something to that effect. Also, I found a room with 4 statues and a brown and green guy who also said nothing. Anything to these yet, maybe something post-game? I tried looking up an FAQ for the game, and found one, but it didn't offer much in the way of help. I saw something about a bonus dungeon, and I think a connection to that guy with the statues, but nothing about the little blue guy.