Is China throttling Google.com?

I do live in Shenzhen, and i noticed that in the past 2 days Google.com is getting seriously slow and unusable. Since it works quite perfectly with my VPN located in USA, i am becoming quite concerned. Moreover Google.com.cn does work perfectly, and all the other foreign sites are at the average usual speed. My main concern is that for all of us, foreigners in China, Google is absolutely a must have, for me is even more, a survival tool. Can somebody in China confirm that this is actually happening ?