The part of the climb between the Archway to Immortality to the South Gate to Heaven is the hardest part of the climb up Tai Shan. Take your time, take plenty of rest stops and try and get in a rhythm whilst climbing. I actually found it worse coming back down again as all the steps affected my knees but they didn't ache afterwards.
This may be a warning or a danger depending on your personal outlook.
Tai Shan is probably chinas largest free for all plantation of giggle weed...
Please remember that this is highly illegal in China and you could get in a lot of trouble for picking plants.
The last cable car down the mountain is at 1800. If you miss it you will have to walk down to the halfway point. This is important to know if you have a hotel booked in Tai'An.
Walking down the mountain in the dark is not a good experience