I've had some customers for big prints from my sugar refinery project, and just saw the first two today. Holy wow, do they exceed my expectations.
My own printer only goes to 11x17, so I've been working with a friend who runs a fine art printing business (we've worked together before on a show of medium-sized prints). Before today I only saw reduced size proofs on cheap paper. Seeing them today full size on Canson baryta paper was a revelation.
These were way better than anything I did with my 4x5, which was my only format for about ten years. My printmaker and thought they looked like they were from 8x10.
I can't make a totally fair comparison, because I've never printed big from scanned large format files. After printing some images both ways, I've come to the opinion that optical enlarging is a sharpness-murdering process, so it's hard to know if I'm mostly comparing digital to enlarger.
My only reservation is that there are sporadic digital artifacts that show up around some light/dark borders and on some diagonal lines. I haven't used enough different digital cameras to know how universal these issues are. They sneak in from time to time, and the only solution I've found is to try to kill them in photoshop with the blur tool. For the most part they're not the kind of thing that a non-obsessive photographer would notice, but that's maybe true for a lot of stuff.