Hi Ge, when I was running patchwatcher, taking the number of patches in the series helped more than it hurt. (It's fairly frequent for people to submit two patchsets, and fairly infrequent for the second patchset to have the same number of patches.) The darn interface needed babysitting, though, since there were always malformed and/or partial series.
I think it'd be cool to have a UI where developers could correct their detected patchsets if they don't like what the automated extractor did. That could morph into a way of submitting patchsets in the first place later on.
It'd also be cool if other tools - say, a buildbot or a patchwatcher - could monitor the detected patchset stream (to save them from having to maintain their own). - Dan