From rolling it will be quicker than any VAG car in standard trim, including mine.
It's the original engine of the ST (pre-bored) but its much stronger because of that!
What about the Cupra R/ Scirocco R? Because I know that both of these cars are quicker from a rolling start than the Golf R/ S3 Counterparts.
I doubt there would be much in it tbh, the R and S3 only lose out slightly due to AWD losses. The MPS offers alot of bang once you are rolling and into 3rd onwards.
I took 2 firends out in it and asked them to compare what they thought to the remapped GTI, In their words the mazda was brutal... and would of left the GTI for dead. As the driver I know the GTI was putting out 265bhp bang on and felt it would have been much tighter.
The reason I ask is because having come across a few MPS 3s, my mapped GTI has had no problem pulling away on the motorway - and this has been against both generations of MPS 3. I've also had a few goes against them at the dragstrip and the MPS although as you say they take a while to really get rolling and get the power on full whack.
I know obviously my GTI is mapped so it's an unfair comparison (although the power is similar) but I'd imagine something like the Scirocco R would be able to deal with them.
I'd also add that when I first had the GTI a gen 1 MPS 3 tried to lose me up a slip road onto the motorway. I managed to stick on his tail and that was with the GTI standard.
Perhaps the DSG has a role to play in these results though.

I really like the MPS, preferred the first gen as the styling was more subtle. I've always smiled when I see them on the road as there really isn't anything obvious to tell you of the nuclear power sitting in front of the driver. I didn't know the 2.3 was the same engine as the 2.5 in the Focus hatches - does that mean that it also is a Volvo engine?