I'd second the other opinions here on
www.eway.com.au. We have been using them for about 18 months now, and have had absolutely no problems with their system and service.
We did a lot of research back then, and eWay came up the best. I liked the way that we didnt have to set up any new bank accounts - they simply hooked up to our existing account. They even did all the hard yards for us in setting up an Amex merchant facility.
Cheers,
Devan