SpinVox certainly has come a long way in the last few years since I checked out their service for converting voicemails to text. They launched at nearly the perfect time. Large vocabulary speech recognizers have been around for a long time, but in the last few years they have become particularly plentiful and cheap.
Also, SMS has taken off in the US to the point that there is now a huge number of potential customers who would be interested in getting the gist of a voicemail texted to them. There is also a fast growing population of users with phones capable of email access who would want the full transcription emailed to them so they could review it and potentially respond. If the voicemail message contains things you might want to write down, like phone numbers, names, addresses, etc., the automatic transcription saves you even more time. Of course, that assumes the transcription is at least as correct as what you would have written down.
Of course, SMS has been popular for much longer in other countries, but language is obviously an issue. Sure there are a lot of potential customers in Finland, but that means you need a recognizer with a very good Finnish language model. But that’s going to help you out only in Finland. Obviously, tapping into a large country that uses the same language as several other large countries is pretty desirable when you are trying to really scale up a business.