An excellent and highly useful extension! I would give 5 stars, but there is a bug in downloading HLS streams with the default MPEG-4 encapsulation (resulting files just about play in VLC, but are quite broken in Quicktime).

(Workaround is to enable the 'HLS as M2TS' option and then convert the MPEG-2 transport stream to MP4 using e.g. Handbrake, but would be nice to see this fixed!)