Hey there Batty. Not sure if you've done any further investigation into what exactly Ivan's Flash is? If not, just enter that into the search box, and you'll have more stuff to read than you'd want to. In short, he reprograms the bike's "computer" (ECU) for better overall performance.
As I write this I am patiently waiting for FedEx to deliver my newly flashed ECU from Ivan. Given that, I can't speak first hand as to what all the difference will be for my ride, but I read enough posts to know that it is THE BEST way to get the most out of your bike once you have an exhaust and aftermarket air filter set up.
From what I gather, it's best to have your exhaust and air filter picked out before the flash so you can let Ivan know what you have and he can tune accordingly.
As others have suggested, getting the front pulley changed out to a 30 tooth unit helps an awful lot with low end chugging. I just got mine delivered the other day and have yet to install it. Waiting to install the pulley along with the flashed ECU and am super excited to take it for a ride once completed.