HP Instant Ink, best ever deal! My neighbour has had her Ink jet printer for 3 years now and has never bought any more cartridges.
Maths part £70 for printer/scanner, so far 3 lots of black and colour carts £0.00, 15 free prints per month, 10 extra prints £1.00 and rolls over to following months as well.
With her low usage she's never had to pay!
You have to be careful... test prints and diagnostic printouts do count!!!
It depends on your usage. I work on projects where I get high periods of usage for say a month, then little for a couple of months. I worked it out and over a year, it would cost me more overall. A key factor is you can only roll over a percentage of the non use.
I would either buy lots of extra pages in heavy use periods, or use pay for a more expensive plan I would not fully use.
Instant Ink is best for people with a fairly constant (or low) use.
Where Instant Ink really scores is if you (say) print pictures using a lot of ink.
When "they" sell ink catridges, they quote as (say) 500 pages per cartridge. This is a bit of a scam as it is based on 5% coverage of page (a full page of text is roughly 10%, and pictures say up to 80%), In other words, you can expect to get much lower number of pages - as low as 120 pages if doing A5 prints (4 times less for A4)!
However Instant Ink is per page regardless of how much coverage, and work out much more economic.
So yeah, for some users it is great, but for others the benefit can be negative - you need to analyse your usage and type of usage patterns to make a judgement.
In the end, I decided to keep my HP Inkjet on normal buy as you need basis. I actually print mostly mono, so I set that as my default, and only need to change black cartridge more frequently. That is another factor to consider with Instant Ink as my pc has high capacity black cartridges.