I began using YouMail on a regular basis when the company offered visual voicemail, which utilizes speech-to-text technology and delivers my voicemail in an SMS on my mobile or email. It's quite handy for those times you can't get to the phone or are on the other line, and even though the speech-to-text technology still leaves a bit to be desired, it works well enough for me to remain hopeful for future releases.
YouMail attributes the growing interest in applications such as the new smartphone-optimized visual voicemail to the rise of the iPhone. I'd say that with several other VoIP services finding ways in which to integrate with social media and business applications such as Salesforce, there's a fairly smooth integration of such tools merging into time-saving services.