I think the comment forwarding would be the most valuable thing here. I agree with Mark and Jesse on the cons of auto-upstreaming bugs.
Comment forwarding would remove the triager as the bottleneck for communication between the reporter and upstream. I make it a policy to always ask the user to register with the FDO bug tracker when I upstream their bug, but unfortunately they do so only about half the time. The other half, I'm in the position of cut-and-pasting questions and replies between upstream and the reporter.
With automatic bug upstreaming, in theory it sounds like a great idea, since the bug upstreaming process takes a considerable amount of time. But in practice it's far from a simple matter. Like Jesse points out, many ubuntu bug reporters aren't knowledgeable in what to include to make a useful report, or add noise to the bug report that distracts from the core issue. So an important step in upstreaming a bug is revising the description, condensing out irrelevant comments, ensuring that logs, backtraces, and so forth are present and relevant to the issue, etc. None of this is easy to do with a script...
However, I do think there are aspects that can be coded around to make portions of the process easier. To pick just one example, in Intrepid we're introducing Xorg-specific hooks for the apport bug reporting toolset, so to file a ubuntu bug against xorg, just run 'ubuntu-bug xorg'. It automatically retrieves and includes xorg.conf, Xorg.0.log, gdm logs, lspci output, and so on. Should save the reporter lots of time, and eliminates back-and-forth between the reporter and the triager. Stuff like the intel reg dumper tool or other special package-specific tools can be hooked in as well.