I'm using an Okidata C7300 dxn in a mixed Mac/Win environment - saw it picked as a PC WOrld Class Award. FYI, it just got upgraded to a faster processor, so the model is now the C7350.
I got it for $1600 with a rebate last year, complete with the duplex unit, a 10GB internal HD, and the Ethernet card include - I think normal street price is about $2200 for the high end unit.
Pages really fly out of it, and it designed to provide solid B&W prints at prices competitive to non-color printers.
With the duplexer, it does process at about 20 ppm in B&W. (I use it to print limited runs of a full color 160 page book that's currently in production, so I often have runs of 6000 pages at once.)
Regarding color speeds, when using the duplex feature and complete redrawing of every page (i.e. collate feature) it does about 8 ppm at highest color setting, and about 15 ppm at a medium setting. Cost per page runs about 10 cents (buying toner online).
An associate has one in a different location, and he ran a non-laser transparency through by accident. It just melted! So he called tech support, he managed to fish out the plastic shards, and it basically ran with a couple of streaks! Since I didn't want those in it I had him order a new fuser for $120, but the fact that it handled such a screw up with minimal damage really impressed me!