Turning a knob in an instrument cluster beats using the mouse to perform the same action on a virtual knob on the screen. But in my opinion the biggest step towards immersion in a simulation is the increase of the field of vision. Seeing more of the simulated outside world has several positive effects:

• Better situational awareness. Everyone who first used PC-based flight simulators and then took up flying lessons will agree: Flying a real plane is actually easier than doing it on the computer, because in the real plane you see so much more. This is particularly true for landings. Judging the right moment for the turn into final approach is easy when all it takes is a turn of your head.
• Better height and speed perception. Only a larger FoV makes the perception of lateral movement possible. The human brain mainly judges speed by analyzing lateral movement.
• Less distortion. MS Flight Simulator, in its standard zoom setting, gives a FoV of 60 degrees. But with a 19" monitor and a viewing distance of 2 feet , your real FoV between left and right border of the monitor is less than 30 deg.! This means you see the outside world through a wide angle lens.

There are many ways to create a larger FoV, but most are for commercial purposes and financially out of reach for humble cockpit builders. I opted for several PC monitors, linked by the program WideView by Luciano Napolitano. Check his website for details. The documentation explanes all angles of this program.