If you are printing anything smaller than 11x17, you are probably better off using your highest quality office copier. But for wide format, popping graphics, or heavy bond paper (such as canvas or vinyl) the Canon imagePROGRAF is an amazing weapon to have in your arsenal. The actual machine and ink is less than my company was paying to outsource our larger printing needs.
If you are using it for large-scale printing such as printing plans as we do, this is a great machine to have in your arsenal. Sure, the size can make it somewhat cumbersome, however it is definitely worth it to have in your office. It allows you to print full-size as well as scaled sheets at a myriad of sizes. It also allows you to scan and download edited drawings which is also a major plus.
We use a third party to service our machine so service-wise, it is hard to say. Support-wise, we have plenty of paper stocked and toner on hand should we run out. In my 4 plus years here at the office, we have had maybe one or two times where the machine was down for a day at maximum and then was back in working order immediately.
Having no experience in printing or graphic design, the Canon imagePROGRAF proved more user friendly and had less steps to learn for basic operation. Now I have learned to use the layout program, as well as routine maintenance (such as changing out paper rolls or ink) without depending on a tech or senior management having to assist me. Super user friendly!
We also use this machine in our office in conjunction with the Teriostar. In comparing the two, the Teriostar is much more versatile. The quality of printing (and ability to print in color) is a big plus for the DesignJet, however, we can do so much more with the Teriostar. In looking at size, they are both comparable in that category.