Some of the more obvious good points of meritocracy is the fact that it aims to bring out the best in everybody. This makes sure that people work hard to get what they want. Generally the more they do, the better off they are. This ensures a society where everyone will work hard. Such a system is especially crucial to Singapore's rapid development from a Third World Country to a close-to First World Country within 40 years.
Since everyone is judged by what they do, it also ensures fair play. As people are not judged based on criteria which would not affect work performance in any way, such as race or religion, people would strive harder and produce better results. It ensures fair play in a field and those that lose out will have to seek other ways to improve themselves, thus creating a better/smarter/more well equipped society.
While meritocracy may seem like a very good system, it does have its disadvantages. For one it cannot be upheld all the time. Certain jobs ARE gender/racial/language specific. Like being a bar host, while meritocracy would allow both men and women to be one, it is more suited to the feminine people. This again is against meritocracy, but still needed in society.
Another example is when working in a Chinese restaurant it would be more authentic to have Chinese workers, not other races as this will make the restaurant theme seem more together, if you have an English restaurant filled with Persian/Indian/Malay/Chinese waiters, the guests wouldn't feel the authencity of that races food/treatment.
Also, in a meritocratic society, the disabled/handicapped are unable to compete on even ground with those more fortunate. In the context of Singapore, the disabled are aided in many ways so that they also can become more competitive. One must also note that in an almost pure meritocratic society, the competition is very intense and the atmosphere can become hostile. This could be a reason why Singaporeans are considered rather unfriendly.