In case you hadn't heard, `Once' is a musical, but don't let that put you off - go buy it or rent it right now. I recommend buying, not least because DVDs are so cheap now - Amazon will let you have this for under a fiver, which is just silly - that unless a film is brand new, renting is starting to look like pretty poor value.
Anyway, 'Once' is a musical like you've never seen or heard, whose songs - and in passing, they're great songs - whether busked on the street or being polished up in the recording studio, are perfectly pitched and completely, naturally integrated and in tune with the narrative. It's also a deeply affecting love story of the kind that life is full of but which are so rarely brought to the screen, full of stumbling and uncertainty but utterly believable - about an affair never consummated, whose complications are left tantalisingly unresolved. Despite concerning itself with rough-edged Dublin street musicians, it's a proper romance, in an almost courtly sense.
I guess what makes it so great is its humanity. Looks like it was shot using whatever the modern equivalent of Super 8 is, so it has a filmic quality but in a very rough way - somewhat reminiscent of the look and feel of those Before Sunrise/ Before Sunset movies, but with none of their preciousness. Full of rough edges and what look like first takes - probably from necessity, but creating a warm, organic quality and a genuine sense of reality. The central performances are beautifully played, restrained but at the same time full of passion and real feeling, and the supporting players are right on the money too. Dublin does its thing pretty well, of course, reprising its performance from The Commitments (where we first saw Glen Hansard, looking a lot more ginger as the guitarist, Outspan)...
Look, there's no point going on about this unpolished gem. Buy, rent or even better, if you get the chance, go see it. Then get the CD - the music is that good.