I use it all the time. Aside from pretty decent international rates, it is also great if you don’t want to give out your real number. You can route the calls to any phone and you can even change it as often as you want – so if your’e leaving the house you can send the calls to your cell, etc. Additionally, when I get a voicemail I get an email with a transcription of the message and the number that called. It isn’t always perfect but it is a great tool.
Keep in mind that if you are calling internationally, the rates are going to be much more expensive to a cell phone vs landline (like 15 vs 2 cents/min).
Good luck