Several more tips come to mind:
1) You can always hire taxis to take you from your hotel to anywhere for day trips. For example, $40 will get from Beijing to any of the nicer Great Wall spots and back. You can even hire a guide and/or coordinate with other tourists at your hotel, if you prefer;
2) If you have an unlocked GSM phone, you might want to bring it along -- SIM cards cost around $12;
3) Don't stress too much about booking all of your hotels/flights/trains in advance. You'll appreciate the flexibility. The only exception I can think of is the 3 Gorges trip (if that interests you) because most boats adhere to fairly rigid schedules and the good ones do fill up.