I have played trombone in a brass band for many years and have had King, Conn, Bb/F as well as a Yamaha tenor trombone.
My reason for looking a plastic ABS instrument is due to arthritis in my hands and shoulder I can no longer bear the weight of even my Yamaha which is reasonably light. I was also looking for a Bb F, so I was delighted to find that Thomann offered this instrument with Bb/F as well as being Gold in colour rather than other plastic colours. I have played it at a couple of rehearsals now as well as at home. On the Plus side, the Gold colour looks like a genuine brass trombone so blends in really well with the rest of our band. The sound is generally pretty good but maybe a little harsh when blown louder. The higher register notes are much easier than lower register. I have used both the plastic mouthpiece which came with the instrument, and also a brass mouthpiece, which I prefer. On the negative side, the slide isn’t the greatest. It makes a grinding or ‘scratching’ noise when played, fortunately not noticed in an ensemble but it doesn’t feel smooth like a brass instrument. I have tried it with the recommended lubricant that comes with it, with water/slide oil, and now using it with nothing on at all. It doesn’t seem to make any difference, perhaps frequent use will make it smoother. I think this is the only down side as far as I’m concerned. It is so lightweight, which is why I bought it, and will give me much more flexibility when performing at concerts as it’s very easy to carry in its soft bag.
All in all, an impressive instrument.