If the situation calls for it a properly installed FBX is a useful tool. I have found the majority of complaints about them are caused by improper understanding of the set-up procedures, coupled with bad (IMHO) instructions in the manuals.
No doubt the majority of applications can be handled quite adequately with a 1/3 EQ, but the 1/60th filters in most FBX's are much better at surgically removing the offending frequency.
FBX should be a last resort, not a first-choice device.
If you have a decent knowledge of sound equipment I'd suggest 1 of the following for mobile DJ operation:
DBX DRPA+
BSS DS26 or DS24, depending upon your system
Behringer Ultradrive
I have used (and will continue to use) some Behringer products, but the analog crossovers in their line are pretty much unusable, as the cut/boost range is only 8db.
The build quality of the DBX vs Behringer is an issue (DBX is superior), but the Behringer is useable if you have few options.
I do continue to see the Composer Pro units in FOH racks and some studios for secondary apps.