Yes, I have a Wellbrook Loop, ALA1530LN. In my experience with it (about 1 year), the lower the frequency the better it performs compared to my other antennas.
On Longwave, I have never had a better antenna. It is good down to the limit of my Afedri SDR (about 50 khz) with no sign of bottoming out.
On medium wave, it is still very good - about equal to my pennant on the top end of the AMBC band.
From 3 to 10 MHz, the sensitivity begins to go down, but not bad and it is still very low noise. It will sometimes beat the pennant and longwire in this range.
Above 10 MHz, the pennant and longwire are almost always better than the loop. None of my antennas are particularly good above 20 MHz.
The loop is about 120 feet from my house and performs best with the null pointed at the house.
On a good day, my noise floor is around -110dBm. Good days are getting to be less common though.