I recently bought this Adaptor because my previous one just stopped charging my (late 2008) Macbook. This new one worked fine...for two days...then it also stopped! I had read all the bad reviews but really, if you want to keep using your Macbook you have no choice but to buy a new charger. I had treated the thing like it was the crown jewels; never kinking the wires, never tugging the connection and plugging and unplugging with the utmost care so when it suddenly stopped working I knew it was not because of any harsh treatment.
For interest's sake I tried my old one again...low and behold, it worked! The orange LED came on and my Macbook started charging. This was very odd - I had tried everything I could think of to make that thing work before and nothing. So I then reconnected my new adaptor, just to see if the glitch had somehow cleared. Nope! The new one still didn't work and the old one still did.
So after a lot of googling on the subject I eventually saw a tip about resetting the SMC (support dot apple dot com/kb/ht3964). That fixed it! This seems to indicate that the problem was not with the adaptors at all but with my Macbook (or possibly the aged battery). So before you conclude that the adaptor is a faulty design (as you might do from reading some of these reviews) consider that many of those bad experiences may be similar to mine and could be remedied with a simple SMC reset.