Canon PIXMA MX 300 printer supported?

Its quite likely, however there is a saying "One never knows until they try". When you buy it make a simple condition that you will only BUY the unit if it works with your setup. Make it clear they understand this so if you decide later to return it you will not have an issue. Some major retailers don't have much problem with this, others will pose challenges and others of course may refuse to honor a refund if the product isn't clearly defective.

Contacting Canon sales and support (they have a phone number and takes pre-sales questions if you have time) will be able to provide you some insight, however I'd figure you'd get more infomation and accurate if you just searched the Canon web site yourself.

Other than that you can always check the Ubuntu HCL list to see if your product is listed giving you a green light, or waiting until someone who's used this printer can respond.

The HCL is found here:

http://www.ubuntuhcl.org/

Canon support for linux:

http://www.canon-europe.com/Support/software/linux/

(** I realize this link is fairly limited, but its the only result from a google. Most of the links are to complain about how Canon does not care about linux support, like this one: http://ubuntuforums.org/showthread.php?t=525112 so take that for what it may. Regardless of the official stance, the linux community has accomplished great things without Canon support so again do what you will with this comment, but if you're looking for guarantee's I'd look at another manufacturer, one that actively supports the linux community)

Thanks Andre Mangan, that solved my question.

HP here I come