Beijing is an entirely different world. Old China and a political capital, the city is wound a bit tighter than New China metropolises Hong Kong or Shanghai. Slow moving, full of people, brimming with culture and bad etiquette, it really is unlike anything else. Dusty, hazy, dirty, smelly and polluted. This is all tolerated to tour its centuries old temples and monuments, purchase goods at Pearl and Silk markets, and experience everything authentic Chinese.
Ten days was a little too long, I think six would have sufficed. Being the first stop on our trip, Beijing really conditioned us to Asia. It overwhelmed, preparing us for populations denser than those at home and humidity. It helped us adjust to foreign currency and it was so safe (a good place to make some mistakes). With experiences such as the Forbidden City and the Great Wall, Beijing certainly has its redeeming qualities. Though for us, we felt it was a nice place to see and a nice place to be able to leave.