It appears that bundler generates the sparce point list just like the SIFT algorithm of VisualSFM does and both bundler and VisualSFM use the same PMVS/CMVS external code to generate the dense point cloud - which is where it gets quite exciting. So its probably not a lot in it. This Visual SFM uses multithreading to speed it up a lot tho and it really hogs that CPU. Theres a GPU version of it too but my GPU wouldnt have the requirements to cope.