1. You can’t select what type of music you want to hear while you are driving a car:

You will hear original musical score and some classical songs from the radio, but you can’t choose or change the music.

2. Run with right trigger (Xbox360) or R2 (PS3):

Instead of pressing A (Xbox360) or X (PS3) repeatedly like in other Rockstar’s open world games.

3. You can’t crouch while you are shooting:

In fact, you can’t crouch at all, unless you are hiding behind a cover.

4. You can’t raise your gun while you are free-roaming the game’s world:

You can’t kill random people GTA style.

5. No inventory system for weapons or anything:

When you start a fire fight, you will only have a pistol. You can pick up weapons lying on the ground, but you can’t keep them.

6. No health meter:

No burgers to eat in order to replenish your health. Your character will recover health when you are not getting hit (Auto health regeneration system.)

7. In-game time progresses when you solve cases:

You may start solving a case in midnight, but the in-game time won’t progress until you make progress in the case.

8. No button to jump:

You can’t jump randomly in the streets of L.A like an idiot. The main protagonist of the game Cole Phelps will automatically jump only when he face an obstacle. Cole Phelps will automatically jump over walls, objects and other obstacles he encounters on his adventure.

The shooting and the action sequences aren’t the best parts of L.A Noire. The interrogations, solving cases, the atmosphere and discovering if a witness or a NPC is lying from his/her facial expressions are what makes this game unique and enjoyable.
Pretty lame