MediaWiki release was briefly installed on the Dutch #Wikipedia. There were several things that made it necessary to roll back to the previous release.
The biggest issue was that the Wikipedia that is number 10 in size and typically uses 1% of the performance, needed considerable more performance. There was a visible spike and there is a need for further analysis to learn what is at the heart of this.
Another issue was that all the parser functions broke. This was because the magic words had been given Dutch translations and the original magic words no longer worked. Tim Starling came up with a solution that ensures that the magic words will always work.
More time will be needed to prepare the roll out for this eagerly awaited release.