Ow, this is the hard question :)
Of the few pull requests that I've submitted in the past, little got merged, eventually. Sometimes it prompted the author to improve something.
It always helps to contact the author directly too :)
I think most authors simple have too little time to actually review those, or take ownership on publishing.
OTOH from the few pull request I got on personal project, I've tried to accept the most of them.
Generally I'd say: the smaller you can make a pull request, the better. branching is cheap, on any of my projects I generally have multiple branches open.
Then again, @work I sometimes create multiple branches per day, each only having a few commits that can be merged into production without damaging.
So I build them up from small configuration changes, utility refactors, leading up to a bigger change eventually, trying to keep the changeset to a minium.
@niels I guess that would be a new flow for you on veejay :)
Veejay is a huge codebase and extremely complex. As I'm not a c programmer, it's hard for me to estimate the work here. But even if you would, say, improve a smallish thing like adding an icon, or improving the writing, keeping it small and simple is the way to go.
@niels I'm not aware, but does veejay have some sort of automated test suite? how would that run?
Just my few thoughts here :)