The k550 was retired.
I have now changed all printers over to HP 5400 dt models at the surgery. All have CISS. No problems with any of them.I was able to hunt around and find the superceded K5400 models at a rediculously CHEAP price $70-$100 at officeworks (scrounged all the stores in Victoria). I would have bought 10 at that price. Even with $130 for each CISS it is cheap.Total running cost for surgery is about $100 per year. Down from $1000+. Plus no inconvenience of replacing cartridges. I have two in my office plus a small epson for envelopes.

I will make the arguement for switching all the office printers to inkjets at my practice.

$350 for each new printer. CISS ~$120.

The cost of one laser cartrige $120.

Savings on cartridges will pay for the new printers and CISS within 12-18 months given that the cost of ink on the inkjets is negligible (plus the advantage of speed and colour and less hassle).

I have changed to HP injkets in the practice and at home, using different models of the 7300 series - an Officejet Pro L7380 at home and an Officejet Pro L7590 in he surgery - the latter has a duplexer for two sided printing, while both do excellent multipage two sided scanning.

Like Anton, I have installed the Rihac external ink tank system (they call it CISS - Continuous Ink Supply System - they are really refillable large tanks) and these are great - refilling with cheap bulk ink is a rare event.