Sometimes Google's voicemail transcription is good enough to get the point across, and other times it's a seemingly random collection of words that only make sense when you're under the influence of really great narcotics. But maybe no more. Google has announced that better transcriptions are rolling out with a 49% reduction in the error rate. This applies to both Google Voice and Project Fi.
Google made these improvements to the transcription engine using a "long short-term memory deep recurrent neural network." Users were asked to contribute voicemails for research purposes, which were used to tune the natural language processing of this system. You don't need to do anything to get the better transcriptions, it should just start working automatically.
As for the error rate, Google doesn't explain what the 49% improvement is supposed to be in comparison to. The implication seems to be that it's 49% better than whatever they were using before this came out. If so, that would be pretty significant.