On madduck's droppings, there is a detailed overview of the diffeernt complaints about Ubuntu from Debian developers
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Ubuntu caused a lot of friction with and for Debian. In discussions with its founder, Mark Shuttleworth, and other Ubuntu developers during (and before) Debconf6, I was able to spell out the main criticisms from the Debian perspectives of the way Canonical/Ubuntu is handling things (without a claim to completeness). These criticisms mainly stem from discussions with fellow developers over the past 18 months, and I largely support all of them. I am publicising them here to help make the status quo more transparent.