What kind of tuning issues would MegaSquirt 3X have vs FAST XFI 2.0?

Not wanting to be argumentative at all - I've never seen or used the FAST stuff, but I also haven't had to tweak on my MS tunes other than deciding to implement more features that I didn't realize I'd want from the beginning. Do other people have to keep tweaking their tunes if they are simply driving them?