This game is AWESOME! It not only feels exactly like an NES game, it's a great game in its own right! Challenging, cool diverse weapons, great music, and while it's hard, it's definitely not TOO hard. All that Contra and Bionic Commando paid off ;)
Also, requirement to press Down to pick up items is brilliant. There's nothing worse than accidentally losing your favorite gun because a powerup was in your way!