I just swapped and flashed mine. As for how different it will ride...it depends on what you do. Flashing it is not the same as tuning it. You can flash it to make many changes (remove top speed limiter, set shift kill times, activate nitrous, select hard or soft kill, change the rev limiter, etc). Other than changing the limiters...if you aren't air shifting or using nitrous....not much changes for just riding until you get into tuning. There might be some gains to be had through some of the other settings I'm not familiar with yet...but after just flashing mine to adjust what I mentioned above...I didn't notice anything. I plan to have it tuned soon.
That's where you adjust the fuel and ignition maps...and build a custom map for your bike..which is where the real performance gains can be found...depending on what you've already done. I'm new to this as well...so take it for what it's worth, but this has been my experience thus far. Hope that helps...