This morning there was quite a lot of traffic on the switch, so i decided to check the usefullness of FOP.
I discovered that FOP (inside FreePBX version 2.3.1.5) was really buggy.
There are refresh problems with extension buttons, when there are more than one call on the same extension.
This is not asterisk bugs, as the BLF keys are working correctly on phones.
I think that FOP is actually more a gadjet than a really usable tool. For such modules, who have not received maintenance since a long time (like ARI), i think that their should be a warning in the module page to inform users that they should not fully rely on them.