Dealspwn
IGN
Gamespot (plus video interview)
Destructoid
Game Informer
OXM
Joystiq
GamesRadar
Ars Technica
G4
Machinima (video interview)
GameTrailers (video interview)
New bits of information:
-40-80% of the environment is destructible, both by you and by the enemy hordes, which will actively break it down to get to you
-Weapons:
--No chainsaw or knife, just the sledgehammer and new melee kills
--New shotgun that fires explosive shells
--The minigun, double-barreled shotgun, rocket launcher, and cannon all return
--No sniper rifle, the assault rifle's scope takes its spot
--Croteam is toying with a Duke Nukem pipe bomb-esque C4 charge that may or may not make it in
-Levels up to 3x the size of First Encounter's biggest
-There's a sprint function
-Retailing for less than $60
OXM said:Most of the changes are incidental, though. Beneath the gloss of the upped visuals and the impressive enemy counts, Serious Sam 3: BFE maintains the same spirit as the original. Levels are still gore splatterfests with wave after wave of monsters gleefully sprinting into the ugly end of your shotgun. Weapons are still powerful as ever with so many great additions it'll be tough for anyone to pick a single favourite. And crucially, the back-peddling, circle-strafing, fire-'til-your-finger-bleeds gameplay of old just doesn't get old.
Serious Sam 3: BFE doesn't do things smartly and it doesn't need to. Croteam's in a genre of one - and with little in the way of competition (Duke Nukem Forever would be its closest rival) they can do whatever they want. They're just having a blast and it's made for a great palette cleanser.