Obviously, one of the best ways to reduce feedback is to try and position the speakers and mics in an appropriate way, but I found that this isn't always possible.
An example is when there is no room (or urge) for monitors and the lead singer turns a PA speaker inwards slightly so he can hear himself sing. With that in mind, I decided to give the FBQ 2496 a go in order to try and get a bit more volume.
I've used it about 5 times now and this has resulted in increased volume and reduced feedback. Perhaps coincidentally, the response from the audience has also improved over this period.
I do find that all the channels get used up during the show even though I haven't heard any feedback. I can only assume it is picking up other sounds and interpreting them as feedback, but whatever the reason, it's definitely an improvement.
The device itself is quite large for this day and age; I'm sure if it was redesigned today, it would be 1/4 the size. So when we're in a venue, I have to find a large table to accomodate both it and the mixer, although I've also sat the mixer on top of it if necessary. It's not heavy though.
I've only used the feedback destroyer features, not the EQ features (I don't think the EQ side of things is very user friendly). For the Feedback destroyer features, it's simple to use; first I clear the values from the previous venue and then it's ready to use for the current venue. I get everything set up at a fairly low volume and then gradually increase the mixer volume until feedback occurs; the FBQ 2496 sometimes takes 2 or 3 seconds to catch the feedback which can be a little annoying to any customers that are already there. But eventually, I can get the volume as high as I need. I tried the automatic setup at home but, after nearly blowing my speakers and hearing, I decided I wouldn't attempt it in front of an audience.
I recommend a case or bag to protect it as it doesn't seem too sturdy; I managed to adapt my mixer case to fit it in.
Overall, I'm pleased with it and it achieves its purpose. I don't know whether it affects the overall sound quality, but we've only had positive feedback from the audiences since using it.
I recommend it for situations where you can't eliminate feedback by normal means.