I used a homebrew version when I was first playing around with end fed antennas for multi-band operation to tame the RF in the shack. (I have my shack in an upstairs bedroom.) Eventually I abandoned the end feds and dipole arrays I was using in favour of a doublet antenna system. However I did use it again when I was first hooking up the doublet as a Marconi 'T' for working 160m but found slinging a length of wire out of the bedroom window did a better job.
As with anything antenna related there'll always be different points of view but just remember it's an "artificial ground" so won't be providing a typical grounding solution and never lightning protection(!)
The following link was the inspiration when I built and used one, handily there's a schematic for the MFJ unit too :-
There's loads of other information on the old t'internet as well.
Hope that helps.
All the best,