Only the early Pi's were built in China. The newest models are manufactured in a Sony factory in the UK, and I believe that very few if any are still manufactured in China.
You are wrong. A very significant number are currently made in at least two factories in China. Look at what Raspberry Pi Foundation representatives jamesh and liz say in these threads: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=62&t=20388 and http://www.raspberrypi.org/phpBB3/viewtopic.php?f=24&t=23248 and http://raspberrypi.org/phpBB3/viewtopic.php?f=63&t=24057
In fact, the Pi Foundation has stated numerous times that they wanted the Pi to be manufactured in the UK from the start, but at the time this was impossible when considering the necessary quality and fixed selling price with little margin. Thanks to the Sony deal they are now able to do this.
Yes, but have they ever said they wanted to manufacture in the UK exclusively? They may have done, but I haven't heard this.
I have a first revision Pi from China, and it works flawlessly. I even applied the highest stock overclock (1GHz) and it's totally stable without any additional cooling.
But have you stress tested it for at least 24 hours by generating a load which is both CPU and GPU heavy? This is essential, you won''t know whether you have a stable configuration or not until you do this. I get the feeling that many people who think they have a "totally stable" Pi actually don't. Some crashes or other malfunctions don't occur until you have been properly stress testing for hours. Also, watch out for overclocking induced SD card corruption.
Also, note that many of the user problems are due to sub-standard power supplies or using USB devices which draw too much power from the USB ports.
Some of these "sub-standard" power supplies that have problems powering the Pi aren't actually sub-standard, i.e. they maintain the USB standard 5 volts ±5% (4.75 to 5.25 volts) when measured at both of the test points on the Pi's PCB while it is under full load. The only reasonable conclusion that can be drawn from this fact is that it's the design of the Raspberry Pi itself which is sub-standard, which shouldn't come as a surprise at this point.
Remember, the Pi does not come with one, so the user has to supply one or buy a third party power supply. The quality of these vary widely. I purchased one that was pre-tested with the Pi and offered directly by the UK distributor and like I mentioned, I've had zero problems.
Unfortunately even this hasn't guaranteed success. I know of multiple cases where power supplies bought as part of a Raspberry Pi bundle have been unable to properly power it.