This is an important article for anyone doing a case study on ONCE for FS6: Independent Films and their Audience. This link refers to a press release by FOX Searchlight. It is worth noting that major distributors like FOX have specialised subsidiary arms, in this instance FOX Searchlight, that acquire the rights to independent (specialist films) and then distribute them in that manner, obviously in art house cinemas or in limited regional or selected cinemas releases.
http://www.comingsoon.net/blog/2007/02/fox_searchlight_picks_up_once.php This brief post in Cinematical also has useful info. on the deal with FOX Searchlight.
A film review on "ONCE"
Amazon would be another good site for critical reception. Of course, read Roger Ebert, too, along with other reviewers. Their links are on the right hand side of this blog.