Not to mention Bazaar, Upstart, Notify OSD, etc. Nothing, really?
Canonical specializes in enhancing user experience, not on low-level stuff like kernel and services. Somebody has to do this, too.
So it's not so bad for Canonical/Ubuntu. But for others working upstream I don't see much benefit.
For ages there were people saying they'd like to see Linux be easier to use. They said this would help adoption of the platform. Many saw the potential of Linux and associated projects and wished it was packaged in a more easily digested way. Thankfully someone came along with a very strong focus on these aspects.
People started to bash them for doing it.
As for the benefit of Ubuntu gaining mainstream acceptance, I think it's clear: the more presence Linux has in the market the more hardware support all of us get, more software, more developers and in general more resources poured into it.
I don't use Ubuntu because I don't like it, but I'm pretty sure I have already benefitted from its growing number of users.
Get over it: Ubuntu is just some glue that sticks and tapes FLOSS software pieces together so that end users can have a great Linux experience right now. That is their contribution.
And it is not as if Canonical creates a lot of software and then turns around not to release it. Yeah OK that cloud thing, big fscking deal... If that makes Canonical have some income than so be it. There is also an official Ubuntu spin that has FLOSS only.
A successful Distro improves Linux viability, especially in the desktop arena.
I agree that many of Ubuntu's features are great. Software Center, Jockey, Update Manager, and most of all, Ubiquity are Ubuntu contributions that have made the lives of many users much easier. But many of Ubuntu's strengths also come from Debian and this has been often forgotten.
The developers of Ubuntu have to understand that even though they are the largest Linux distribution, they still have to contribute back to the community. I go around and see Debian, Red Hat, and Novell developers everywhere contributing to the core projects and drivers. I have seen VERY few Ubuntu developers. They seem to be on their own little island and have pretty much stopped talking to the general Linux community.
Ubuntu has to understand that even though Ubuntu is the largest Linux distribution, it is not the entirety of Linux. And they have to do more than just backport code.