Feedback Eliminator

[Roy Dennis]

Does anyone use a feedback eliminator ?
I have been thinking of purchasing an OMNITRONIC FEEDBACK ELIMINATOR
Most of my shows are in small to medium sized bars where there is no stage and cannot position speakers very far from singers. I use radio mics which means singers sometimes wander nearer to the speakers.
What I am asking is,
1 are these things effective ?
2 do they require a lot of adjusting during a show ?

The one above is supposed to have an auto mode and it does have XLR input and outputs.
I use a pair of active speakers coming from a mixing deck.

Any advise and recommendations please.

Roy.