I agree on some things here, but not all.
The thing is that Epic tried to make it cover based, but People Can Fly shone through and made it so that it wasn't nessecary. My favorite tactic involves slide kicking someone, blowing their torso off in mid air with the shotgun, and kicking their two parts into a deathtrap. Oppurtunity? Not extremely often. Fun as hell? Totally.
Although, did anyone else notice how short it was, or is that just me. Seriously, I finished it in two days. It was definitely worth it due to how much fun it was.
The dialogue was so immature but still hilarious, such as a conversation along the lines of:
"If you come near me again, I swear, I will kill your dick!"
"...What? You're going to kill my dick? What does that even mean?! Fine, I'll kill your dick!"
*awkward silence*
"Now, if you two are done with the dick killing we have more important things to do."
Also, glad I'm not the only one who remembers Doomguy's physics defying awesomeness.