I could write a book on what we learned in China over the last few weeks . . . but I'll just try to address some of the questions above.
miselemeas - Shanghai, Beijing, etc . . . are all very manageable on your own without a guide. Taxis are straightforward, plentiful and cheap and they all have to give you a meter receipt so there's no mucking about with off-meter charges. Pickups cost about €1 to €1.20 (depending on the city), but after that the meter clocks up very slowly. We took loads of cabs and our most expensive one was €3.40 after about 30 minutes driving through heavy traffic.
We found Beijing to be just a tad . . . boring. There's something about it that makes it look too clinical. We did the great wall, Tiananmen Square, Forbidden City, Temple of Heaven, etc . . . and they all looked like they had been rebuilt in the recent past. The net effect was that the 2-300 year oild buildings we looked at were just too 'clean'. You really didn't get the impression of age from these places. Shanghai is a different kettle of fish altogether - the city is on a different scale (human instead of Communist) and has a lot more to recommend it.
If you are bringing kids then PM me and I will give you more pointers.
madmoe - we stayed at the Astor House Hotel in Shanghai. It is within spitting distance (2 mins walk) of the Bund. It is very definitely old-style and gives you an idea of what colonial hotel life was like. I would suggest just going to Shanghai and taking it from there yourself. There is plenty to do and if you pre-book a trip you may find your plans have changed by the time you get there.
madmoe1013 - agree that Beijing and Shanghai are like cheese and chalk. Hong Kong was in a different league again - it is the only place I plan on revisiting in China. Due to a change in schedule we only had a few hours there, but it looked amazing.
z