Have 5 MP C5503s for the past year with close to 1M pages printed across the fleet. Agree with some of the posts above.
Pros:
Cost - Lowest rental and cost per print when we went out to tender.
Support - Great initial training, engineers visit with 4h, however if you get any printers included as part of an agreement there will be lots of head scratching by them.
Supply Ordering - All supplies can be ordered with a couple of clicks via their portal.
Reliability - Only one of the devices has required engineer visits, and that's when one just spat all it's toner everywhere inside requiring 2 days engineers time and many many boxes.
Drivers - Drivers are hugely customisable. Being able to have only hold print available at the driver has reduced waste no end. Also works well with the Google Cloud Print beta installed on our print server.
Cons:
Managing address books across devices can be fiddly
Device Web interface is slow. Often get device in use please try again when trying to save changes. It helpfully forgets your changes so you have to go through the process again.
Warning Lights - As @dhicks mentioned, they like to flash lights when at 20% and yes with 4 bottles they will be doing it a lot.
Some of the cons may not be an issue with papercut though.