Hi Liz,
Kindle seems like the best compromise client for e-book readers at the moment if you are located in australia.
I travel frequently with work and used to take my sony vaio with me everywhere along with my datastick and notebooks.
My Sony now stays at home and l only take my IPAD. It is brilliant. I only carry one small item and I have global roaming 3G access to anything anytime. I even have full access to my work Citrix farm and home remote windows 7 desktop
I have found that the IBooks reader for the IPAD is very good in terms of ebook formating and the IPAD is a great format for portability and screen size.
The only problem is access to actual ebooks. Many of the copyright laws seem to keep access to the large volumes of ebooks restricted to US or Europe regions.
The online store for iBooks has a very limited selection of books. The Kindle client for IPAD/Windows has a larger selection of books.
Interestingly enough NOOK (Barnes & Noble) has the largest amount of ebooks online but the least amount available to our region. Nook also seems to have the best converted ebooks (not all converted ebooks have the same quality conversion).
The reckon the best alround system would be to have a Nook PC Client with an American Account then upload these into the iBooks reader
If you are looking at options I would give serious consideration to an IPAD2 with Kindle & iBooks client.
Cheers