Da Bomb, Da Keeper, Da Lock, Da Big Cheese, the one printer period!
22 April 2013
Summary: It's a freaking miracle. Bought a used duplexer, a used HP JetDirect J3111A for Older Mac compatibility as well as ThinNet Ethernet and a second twisted pair port (had an 8000 N that I spilled Coke in and couldn't afford to repair) and with the spare 8MB module from the 8000 N had everything you could ask for except a third paper tray, which like the printer itself minus toner (the brand X toner it came with failed promptly), duplexer, and the J3111A card was an eBay...
A workhorse. These printers will work for years with proper maintenance.
23 March 2012
Summary: This is my second 4000 series printer. First is working every day for last year and printed over 100k pages without any issues. When it starts jamming, replacing blue pickup rollers solves misfeeds. Duplexer is a must accessory, will save on paper. My LJ 4000 was manufactured in 1997, making it 15 years old, still it has lots of life left. Another plus is availability of parts and affordable toner cartridges.