Yes the Telstra roaming charges were ridiculous, They were $15 / Mb now reduced to $3 but still crazy.
The Global Gig is fast enough for Skype, I use an App called Viber on my iPhone which is great and allows unlimited free phone calls anywhere in the world to another person with Viber. (with better clarity than regular phone calls)
I monitored a few phone calls and chatting for an hour on Viber, USA to Australia only used about 60 Mb of data.
Considering you get 5000mb per month allowance with Global Gig, it is plenty to call home each day for an hour, emails and web browsing.
Viber and Global Gig are saving me thousands every year now compared to using local phone cards to call home as I did previously.