Once the printer is on its stand, you can get through narrower doors by lifting the front cover and the (forget correct term) eject tray - saves a couple of inches.
Printing over ethernet seems more reliable and faster (macpros 10.6 - 10.10).
Clean inside regularly (inside the printer, and the surrounding area), the cutter builds dust with papers like Platine rag, and this is best removed, to keep the new girl happy.
There are times when you'll need her to forget things - this involves powering off the printer, and turning off at the wall for 10 minutes. This gets easier if you cabletie a surge protector outlet (with a power off switch) to one of her front legs.
Initial calibration is important - look through the list of approved media, and ensure that you have / can get a stock of this - allows you to remind the printer how to behave.
For curly papers, you can keep the top cover open by blocking the receptors for the cover using several bits of mount board bonded together to get the correct thickness to make the printer think the cover is closed. This allows you to baby sit (naturally, with cotton gloves) the first 6-8 inches of an otherwise unruly paper.
Our 8400 sits around eight feet from me - I don't find the noise an issue (though it is useful to hear it finishing printing when I'm not in the room). Wouldn't say it was that much noisier than our 3800 or 9800. However it does make the odd clunk when waking to perform maintenance ,which can be disconcerting in a quiet space, late at night.
Distrust the inkremaining indicators - not just on the starter carts. Remaining ink can drop from 40% to ink out over the course of half a dozen 40x60" prints. You can avoid this problem by keeping spare carts of ink on the shelf (and if you don't have spares, by not planning to print on a Friday evening or weekend). If you're on a PC, then the accounting software keeps a very fine track on materials costs, and you can add the costs of your papers to the equation. Used it extensively on the 8300 to establish actual production costs(had an XP parallels installation just for this (well and the Nortel systems)). Why this very accurate ink usage can't be utilised by the ink monitor is anyone's guess.
If you get a warning about the print head, don't run multiple cleanings, without printing inbetween. I find a Granger rainbow seems to force all colours through). If a first level clean doesn't fix things, call your vendor - odds are you'll get a new head delivered in the AM (or sooner, if your rep is really good).
When you find papers you like, get them in a range of sizes - we carry 17, 24, 36 & 44" rolls of the most popular papers. This allows for the most effective media usage, and helps you (well, me) to speed up printing, as there is no hanging around to find that print that fills the otherwise wasted paper.
Don't judge a print for the first 15 (or30) minutes - they tend to dry down / shift more slowly than the Epsons. That said, this time can be very effectively spent making and consuming coffee. That said2, when a print is right, it looks so the moment it is coming out (most pleasing).
If you run the printer with lid open, keep small children and clients away (or severely warned) that the print head will not notice their fingers as it wizzes back and forth, and that they should not point too closely at the wonderful details coming out.
Late one night, you will tell the printer to eject paper, rather than cut. (We) Keep a razorblade just below the control panel, on a bit of magnetic strip, to enable the safe removal of the print. See previous point about stern warnings to clients, children (and self).
Enjoy the drama that you get to produce!
Oh, and remember that the larger carts can be referred to as bottles - 700ml, and almost exactly the same price (at least in the UK) as vintage Krug.
(OK, that was a bit longer than I had imagined)