can the 05-06 key fob be programmed for a 04 coupe?

No.

Why not? I don't think the remote has changed.

prob......but its not worth the hastle

i don't see why not. I programmed my brother's old keyfob (came out of an 03 maxima) to my 05 coupe and works perfectly fine and might I add looks a bit better!

So how does that 05-06 keyfob work exactly. I got the 6MT so I can't have it, but I don't understand the keyless start function. I saw one the other day, and there's no push button to start the car, and I noticed the ignition looks funny. Almost looks like you still have to turn the ignition, but you don't have to put the key in?? I've just been wondering about that...

nope

key fob has a radio transmitter - i.e. you can leave it in your pocket, it detects when you are near, lets you enter (via code) and start car (all while your key fob is in your pocket).

Was the original poster referring to the Intelligent Key? I was just commenting about the standard remote.