Every mower, just like any cutting tool, works better when the cutting surface is sharp.
When your mower blade is sharp and in good working order, then the mower works with less effort and is more efficient.
A dull blade rips and pulls at the grass.
The grass doesn't get a clean cut so part of the grass blade tries to wrap the mower blade.
The shear momentum of the mower blade then tries to pull the grass up by its roots.
The internal forces end up just ripping the grass blade at its weakest structural point.
Multiply this by thousands of grass blades and you can see that more power is needed by the mower's engine
to cut or better yet, rip your grass. This produces more wear on your mower and decreases life.
These forces work pretty much the same wheather the mower is a reel or a rotary type mower.
Sharpening Mower blades is fairly easy to do even by a novice and you will master the task after two or three sharpenings.
You should expect to sharpen your blade at least twice during the mowing season.
Rotary mower blades are the easist to sharpen since there are really only two cutting surfaces per blade assembly.
I find that the hardest part is really getting the blade off the mower, other than that it's really fairly straight forward.
Of course SAFETY is paramount whenever dealing with any power cutting equipment.
So, don't do any of this while under the influence of anything that could alter your concentration, such as alcohol or drugs.