Car and Driver magazine in the USA managed a 5.3 0-60mph in the Forester, which was quicker than they have managed in the WRX.
I've beaten a couple of WRXs away from the traffic lights (just) and it was not as if they had been surprised or anything, as they were beaten several lights in a row.
The dyno sheets coming in from the states seems to indicate that Subaru have underquoted the kW and Nm on the Forester, or have quoted 'hot' values. (30+ air temperature, where you notice that power is down)
But, if you like Subaru's figures, the Forester XT auto is quoted as quicker than the WRX auto.
Also note that the manual WRX is 30kg lighter than the manual Forester, while the auto WRX is the same weight as the auto Forester.
If you have a look at the dyno charts in the technical articles on the Forester, you will see that the torque and power start lower on the Forester, meaning it is much easier to get off the line, which is probably why (with your average WRX driver) it is possible to beat them in the traffic light drags.
When it comes to the twisty bits, the WRX is going to be the winner through the bend, but watch out as the Forester leaps out of the corners as it's easier to keep on boost. (mind you, with the STi springs, and struts from a WRX on the Forester, they have been found to corner extremely well.)
And yes, I own one. (let's not get started on the insurance savings)
rob.