Yes but it takes a little learning. I would say that most people will say that they hear no difference the first time that they switch it in. As SPL say in the manual " This is not an effect".
To set it up you use the controls to move the sound image in your head so that it resembles the image heard sans cans. So , as a rough example, if your left speaker produces an image , say, 30 degrees from centre but on headphones you hear it as 45 degrees coming more from you left ear you can shift it back to 30 degrees on the cans. Note : it does not make the sound appear as if outside your head. It can provide a wide, deep and continuous soundstage in your head.
Once properly set you can have the heaphones and speakers on simultaneously. Listening on headphones you can then remove them yet the images heard on speakers and headphones match. I am impressed every time I do this. This enables its prime purpose which is to allow producers to mix using headphones. But it is great for home listening too.
The downside is that on some material with the matrix switched in there is a small reduction in bass drive. You need to weigh this against the naturalness brought by the matrix. Of course the matrix can be removed or reinserted at the flick of a switch.
There are other Phonitors in the range which include DACs etc. These are aimed more at home users but the crossfeed matrix is not as sophisticated as with the Phonitor 2.