I'll preface this with I now own 2 different copies of Boondock Saints on sd dvd, and I bought the bluray also.
The bluray isnt that much better than the dvd;
review;
Fox presents 'Boondock Saints' in 1080p/AVC MPEG-4 video (2.35:1). Both the theatrical and extended cuts of the film are available from the main menu, via seamless branching. This is the first high-def release for the film, and unfortunately it's not all that impressive. This does offer some upgrade over the standard DVD, but I didn't find it substantial.
The film's source remains sketchy. There is heavy grain in spots, and a fair amount of print defects, including blemishes and dirt. Black levels are solid, and contrast a bit hot but otherwise well balanced. The image only pops sporadically, hampered by scenes with limited depth and visible fine texture that wavers from shot to shot. Colors are nicely saturated, however, and relatively clean. Fleshtones are generally warm. Finally, Fox has produced a nice encode, and despite the grain there is less noise than I expected. All in all, a decent if far from great high-def transfer.