It erases the emotions associated with painful memories. Not the memories themselves. You won't forget what happened. It doesn't have anywhere near the same potential for abuse a drug fitting the headlines would have (à la MIB).
When the memory loses its potency, it becomes just another passing detail. It doesn't have any power over you, it will not haunt you, and in time can be forgotten.
Judging by your username, I'm going to guess you are familiar with the operation of DRAM: it must periodically be refreshed by reading the data out and then writing it back in. Human memory works the same way (albeit without the requirement of continual refresh). The drug in the article interrupts the write-back process, and the memory is then lost.
Still, a better understanding of the chemical association between event memory and emotion is very interesting. Even if it's not used to develop widely available drug treatments, being able to manually and precisely knock out the link has great implications for developing effective psychological treatment of PTSD, depression, etc.