For my purposes, not to rush out for. From examination of their two profiles that could be of most interest to me, the gamut volume of the luster product is about 9% less than Gold Fibre Silk for Epson 4900, the Black point is similar at L*4. The white point has a remarkable -8b value (blue); that's worse than Epson Premium Luster. The gamut volume of the baryta satin product is 10.6% less than IGFS and the Maximum Black only L*10. Didn't examine anything on the MK side.
I am just testing all samples they make. Profiles form Sihl web page are not ideal, quite non-linear (3880).
Baryta Satin is not comparable to IGFS - it is diferent look and feel paper, balcks are not so deep, but results are really good for B&W - analogue feeling (using QTR and OEM inks). Some people like it, some might not. Min L=7 with QTR (3880).
Both cottons are to warm for me and not very contrasted (only Sihl profiles used). But could be really good for aquarell-like landscapes etc.
Haven't tried matalic yet.
Luster is, indeed, a little bit "radioactive".
Hope it helps.