exited my aussie trade @ .65799 with $187 net profit
usman, yes you can trade everything in IB, including forex.
The margin for the 100,000 aussie that I just traded was $1,500
for 100,000 cable margin = $3,500
for 100,000 EUR margin = $2,800
etc, etc
To check it yourself, open up your IB TWS and add the symbol
GBP and then in the pop up select GBP.USD (IDEAL PRO) <- (very important, it has to be idealpro)
Then just enter a trade amount but don't transmit, just right click and chose "Preview Margin/Requirement" it will show you required margin.