When I have installed a game on the 360, and I click on the standard "play game" at "My Xbox", does the game play from harddrive or do I really need to click on "play from harddrive" to do so?

Thanks.

No you can just play it without choosing it.

Alright, thanks. I'm not noticing any significant loading time decreases though, Left4Dead still takes freaking long to load.

Depends on the game. Some load faster, some don't.
At least it's less noisy and the drive can't scratch the disc :)

Game like Fable 2 had faster load times but there isn't much of a difference in most games. I mainly do it because it's not nearly as loud.

But you guys are sure there is no difference in selecting "play game" and "play from harddrive" when installed?

Nope, there is no difference. Once installed, it will always play the game from the hard drive instead of the disk.

If its installed it plays installed automatically regardless of which option you use.

Mine's as quiet as a mouse and some games defo load faster.

L4D 1 & 2 both load slowly on PC as well..

Now if only there was a way to have it not require the disc once installed...