The trip itself is a great experience. Definitely something everybody should do. Amazing views all along the trail. Sometimes it gets a bit hard, mostly because of the height. But you don't need to be a real hiker to make it to Machu Picchu !
One thing must be said though, it does give you a weird feeling seeing all the porters running around with way too heavy backpacks. Of course you will never find out how they experience it all and how their situation actually is.
The arrival to Machu Picchu is the biggest rewarding for all the hard times during the 4 days of hiking !