The Skype system will allow messages to be left and picked up at my convenience.
I tend to use my Mac Address book to the fullest, Skype can access this so making called is so easy, I do a search and up comes a list of all the contacts for that person, Skype, Mac so cool, and of course its the cheapest call ever, I phone the USA and Canada a few times a year, and the call is routed through the internet to the cheapest method.
Some times I like to use my iPhone, its known to many and they see me light up their phone, but working and holding a phone is not so compatible, so I use the address book and find who I want to talk to and click the phone icon, this calls via my iPhone and I can talk hands free, ok I can do the came direct with the phone, but the Mac adress book is so much easier I think.
Thats it, my mobile office coms system, all rolled up into my mac and Skype. I have tried Google and yes it does work well, but as I am Mac oriented, !!!