The Canon Pixma G640 is a value-for-money machine. This particular machine can produce excellent photo results, although it suffers from the common issue of paper feed marks, like most printers under 1000 Euros. However, with prolonged use, this issue may improve. Now, as for the inks, it is a thicker Dye Based Ink solution, resulting in vibrant colors while also properly adhering to most papers, even plain ones! Of course, not as much as in photo paper.
The printer is very picky about the type of paper used, and 99% of the time, it is a paper-related issue. If you prefer more cost-effective inks, I would recommend looking in Germany, where Canon sources their inks for these specific printers.
Objectively, the printer has the ability to produce more colors and tones, as well as more detail in these colors. This is not only due to the 6 inks but also because its print heads support micro-nozzles, which are approximately 384 for each color. In comparison, Epson printers, for example, only have around 400 micro-nozzles for black (for text, etc.) and around 128 for colors, and not always consistently.
Micro-nozzles are the tiny holes that release droplets of each color when sprayed onto the paper (combining each color to achieve the final result).
The supported inks will last you a considerable amount of time, but it would be good to have a second set on hand in case one runs out faster (always source them from Germany, avoiding non-genuine inks from China and India). Objectively, one bottle is equivalent to about 14 of the old ones we used to have, but for the same price. When filling it, make sure to press it slightly before closing it to create a vacuum and prevent oxidation.
Never expose the inks to UV or Blue Light, as they will deteriorate. Print at least one full-color page (e.g., photos) every week to keep the ink flowing through the tubes and prevent clogging.
Other positives: Removable Print Head (Right Head and Left Head), Quality Inks, Competes with Photo Prints, Prints up to 300gsm, supports Gloss, Matte, Fine Art, etc. It has a scanner, but it is average (600dpi). Ideally, the G540 without a scanner is recommended for purchase.