I just recieved my 3800 on Friday along with a few sampler packs. Obviously, I have many of the same questions you all do.
I got to print ~3 images on 20 different types of papers. It was informative, but I still have many questions.
The test prints I did included several Epson, Red River, Pictoric, Hahnemuhle, Inkjetrt Ceramic, and Crane papers. I tried a few of each of the major paper types.
It may be that my brain is stuck on this, but even under glass, I am very aware of any texture on the paper. This may be because I am used to seeing High Gloss prints so seeing any texture is distracting for me.
Also in comparasion all the papers I tried with the 3800 had less Dmax. The Gamut was good on the 3800, but the DMAx was lower, even with Pictorico High Gloss Film.
I have basically broken things down into 3 categories (Darrell's World). they are Glossy, Luster/Fine Art, and Matte. Here are my favorites so far.
Glossy: By far and away, send it out to WHCC or MPix. The Lightjet prints crush any glossy work coming off the 3800. If you can prove me wrong on this, please, please, please let me know. I would love to find a good Glossy solution ont he 3800. Compared to Lightjet type prints all the 3800 glossy looked like Semigloss.
Luster/Fine Art: I prefer as littel texture ont he paper as possible, so my favorite so far was the Hahnemuhle Fine Art Pearl. It had a subtle texture, a pretty high DMAX, accurate colors. BW prints look nice on this as well.
Epson Luster had too much texture for me. The Ceramic Luster was a little better as it looke the same as the Epson, but the texture was the slighest bit smoother.
I tried the Crane Museo too, but that had a strong texture that reflected light from every angle. I could see people liking this for BW work, but it borders on gimicky/fadish. Its ok as long as you are the only one in your area using it. ;-)
Matte: Epson Matte is good for proofing, but the Hahnemuhle is my favorite matte paper so far (albiet I haven't tried many papers). The Hahnenule Rag Mat is smooth and has a high Dmax for a matte paper.
Well, there are the highlights of my weekend of paper testing. I obviously have a strong bias for the smoother textured papers and thos with high DMAX.
I am curious to hear more comments about the best papers for "under glass" viewing.