Most of my sales are dye sub metal prints, which I source through Imagewizards and Bay Photo. They work especially well in large sizes (where the slight softening caused by the dye-sub process is irrelevant) and with contrasty landscapes and cityscapes.
I wouldn't use them in small sizes. The dye sub process introduces a very slight softening (so the print images need to be sharpened a little bit more than for an average glossy print) but, in absolute amount, this softening is the same whether the print size is 6x4 or 60x40. So, when printing large, it translates to no real softening at all, yet, at the smallest sizes, it can result in lost detail.