Standout points from conversation with Sandy Armstrong:
Lack of communication with upstreams on bugfix/patch policy. (esp for SRU)
Frustration when bug reports do not make it upstream soon enough for a timely fix.
"I would rather not spend any time at all in downstream bug trackers." In other words, we should think of zero UI exposure as an explicit goal.
"Sometimes I think it would be great if I, as an upstream maintainer, could make the decision that all Launchpad bugs should auto-forward to GNOME bugzilla. This would fit well into my personal bug workflow in a way that switching between bugzilla and Launchpad does not." (note that most upstreams do not request this, however; Sandy appears to be an outlier on this one)
For Sandy, the line between Launchpad and Platform is fuzzy. For example, SRU policy is a major concern of his. Tomboy had some needed bugfixes that did not make it into an SRU, or came close to not making it in, because although they were "safe" changes from Tomboy's point of view, they set off some red flags for Canonical's SRU maintainers. If this is a widespread problem, perhaps there are things Launchpad can do to help SRU maintainers make decisions that more closely match what upstream wants (when upstream is being reasonable, anyway, which in this case it appears they were -- they just weren't matching the way SRU expected things to be delivered).