Makes it a bit tougher IMO, but an experienced player probably enjoys the extra challenge. I've enjoyed using LF/CF/RF but I don't think I'd want every league I participate in to have those parameters.
I play roto and try to max out my games played at every position, and that gets more difficult with the more discreet positions you use. You need too many back-ups, unless you have a solid bench player who can play all three OF spots.
Doesn't change the game too much. Gotta set the rule before the draft though, obviously.
* Steroid induced record