I agree with you about Duren - it is a lovely organ and the quality of the sampling is much better than Piotr Grabowski's earlier, free sample sets. I have very much enjoyed playing it and it has become one of my favourite sample sets, too. I love Poblet, but I would have preferred a closer microphone position. I think Prof. Maier optimises his sample sets for headphones, and some of them sound too wet in my system (multichannel studio monitors plus subwoofer). Duren sounds better to my ear, and has the advantage of being multichannel and with variable perspective.
I bought this as soon as I had heard that it had come out, and I gather that I was Beauty in Sound's very first customer when they became the UK distributer. Rather annoyingly the price was reduced in Piotr's winter sale a few days later.
I would not say that Poblet and Duren are direct alternatives. They both have the Metzler sound, but Poblet is conceived as a "Bach organ", i.e. inspired by the Baroque organs of Thurungia and central Germany as exemplified by Trost, in contrast to the better known North German and Dutch style of Silbermann and Schnitger. As it is located in Spain it also has a trompeteria with fiery Spanish reeds. Duren has some French Romantic leanings, and it seems to me to be quite a flexible instrument.