Fxx is abused just because it is unclear how BPM translates to the actual speed pattern for most people, and many other trackers simply do not have BPM at all.
I actually disregard BPM when composing, and just tweak the speed and the tempo until I like the speed obtained...
The tracker's way to get BPM is through a math formula that doesn't consider the notes input, therefore you can have a 600 BPM song that plays reeeeeallly sloooooooow...
