I too am with 3 in Australia, but I have a data plan. Which without I would find the N900 rather lacking as it is an internet tablet with a phone rather than a phone with internet capabilities. However, what you do with your phone is up to you. :-)

WRT Skype on 3, they offer free Skype to Skype calls (unlimited at the moment I think) but you have to use their version of the Skype client:

...
http://www.three.com.au/skype?c=Page...=1221530684029

I don't really think this is a Nokia issue as Skype is already integrated into the phone natively.

I can also recommend whirlpool as a good source of all internet related things within Australia
http://forums.whirlpool.net.au/forum/114?g=138

I would really recommend a data plan - you will find the phone so much more fun!!