Comment 12 for bug 376092

The upstream report is supposed to be complete, so that the upstream devs don't have do fiddle around too much to find the necessary information. Of course, there should be a link to the ubuntu bug report (if there is one, it is also possible to report directly upstream if you know what you're doing) for cross-referencing.

That being said, the bug reports are not really duplicates. At the ubuntu level, we know what versions of the driver are included in different releases (upstream doesn't), what kind of tweaking has been done to specific packages, etc. We know (well, think we know) what information upstream requires for different kinds of bugs, and if some newer packages need to be tested before reporting upstream. Usually, a ubuntu bug report will be much more messy than the upstream report. We then forward the relevant information upstream when we think we have all we need.

In your case you pretty much got everything right in the first round (including testing with newest development snapshots), so it could more or less be upstreamed directly.