If you want to know about the state of the MediaWiki localisation, there are the group statistics. If you want to know how a particular language is doing, there are the language statistics on the Portal for a language. These are the statistics for the Indonesian language.
Statistics are nice but it is too easy to get too much of them. When you are an admin of a Wikipedia, the most you want to know is how is my language doing and what does that mean for me.
Yesterday a message was posted on all the Wikipedias informing how their language is doing. Many localisers went to translatewiki.net and as a consequence of the work done yesterday and today, two languages are now fully localised, for several languages all the "most used" messages have been localised and, tomorrow all these localisations will be live on all the WMF projects.
Statistics help in understanding the status quo. They provide arguments about what to do next or they provide the yardstick to measure our accomplishments by. Both are important, but learning what to do enables people to make a difference.