I recently looked into this as i was thinking about iPad for trading. The shortest answer i got was "NO".
The iPad can't support the Javascript even if you go down the Jailbreak road. From what i was told, even some of the MacBook's still won't do it unless you have the latest Apple OS.
In a way it isn't fair as over in the USA, E*Trade has a brilliant iPad Trading Platform that they refuse to port into the ASX.
A lot of companies are still struggling to decide whether or not to jump on the iWagon or remain concentrating on their proven markets.