After looking at reviews from Tripadvisor decided this would be the best part of the wall to see. Arranged a regular taxi to take us for 700RMB (could've haggled it down to maybe 400 we found out later but didn't as thought it was fair price anyway). Taxi took just under 2 hours from the centre of Beijing and the driver then showed us where to get tickets, etc.
Took ski-lift up and tobaggan down - total cost including rides up and down, wall entry and compulsory insurance was 101RMB.
If I went back again I would take the cable car up then walk along the wall to the tobaggan down as there is more downhill this way and that route would form a natural triangle.
This is an interesting section of the wall as it's so varied with steep climbs and then lesser ups and downs. There's very little flat so if you're not prepared for it you won't get very far.
We spent nearly 4 hours in total on the wall walking along the wall in various directions. If we had gone on a tour it would have cost 600RMB for 2 people and we would only have had 2 hours actually on the wall so very glad we took the taxi and had the freedom to spend as long as we wanted.

Not only is this the best part of the wall to visit, it has the greatest decent of all the other sites. As you have heard from other reviews, Badaling is not the place to go. They are building 5 star hotels near Badaling so that should give you an idea of how crowded that section of the wall is. Mutianyu provides great "people-free" photo opportunities. I can't say enough about this section of the wall.

The best way to see Mutianyu is to take the closed cable cars to the top, once you reach the top, take the left route, you will be able to make the steep climb to the highest point on the wall, but if you are not so adventurous, then you can walk left for some great photos without climbing the steep wall section, work your way back past the cable cars and walk all the way to the ski lift / tobogan area (this walk is mostly downhill), TAKE the Toboggan down back to the parking lot area where you began. This is such a great way to end your hike, Don't worry, you can control the speed of your descent!!!

If you go to the top via ski lift, just be aware that your walk will be about 80% uphill, everyone I passed walking this way were disappointed to know that the other route was better.

When planning our visit to China, I checked tripadvisor for information on what to see and do in Beijing. Some people recommended going to the Great Wall at Mutianyu. This was fantastic advice. My son has been to Badaling, and did not enjoy it due to the large crowds of people. He did enjoy Mutianyu. There are two aerial rides up to the wall. The aerial chair lift drops you off next to the toboggan ride should you not want to walk very far. The aerial tram is further away, but we (60+) were able to walk in mid August, the distance from the drop off of the aerial tram to the site for the chair lift and toboggan ride and managed to ride the toboggan down. It has breaks so you need not fly like an Olympian, but can if that is your desire. The toboggan was quite fun, not nearly as frightening as taxi cab rides in China.

I was just at Mutianyu and it was really a pretty place, worth the visit. like other people here, I have gone to other sites of the Great Wall, but this was the best one and the say was perfect!