It is quite understandable to see ratings for this movie score from top to bottom. Yes, it is slow and there are scenes where frankly nothing happens (only in the viewer's cerebral reckoning). The use of Spanish/English dialogue is not too much of a success. Hand-held camera photography and some grainy texture to this remind one more of a documentary than conventional film. And the point of the mirror scene with its homosexual connotations is not all that obvious especially when it is not tied to any ensuing character or plot development.
And of course the ending, which has been revealed on reviews elsewhere,is completely unacceptable to viewers. And the continued dialogue as the end credits roll is anathema to many. So yes, the disparaging reviews and low ratings come as no surprise.
There are saving graces however. The performances, not just of the principals, are very good. Tim Roth is excellent as one might expect. And most interesting was the portrayal of Arnulfo and Carson who really came across as barely kids out of their teens, their boyishness amply displayed by the horseplay in which they engaged. Arnulfo's attempts at playing tough from the outset are in stark contrast to his whimpering, sobbing behaviour towards the film's end.
A further plus to be garnered from this movie is the way in which the 'baddies' are portrayed. Those involved in gun-running are no stereotypes villains in the Hollywood sense, but nonetheless capable of sudden violence. The scene in Arnulfo's uncle's kitchen is a highlight of the film as events move from the mundane (washing up and clearing the table) to murderous violence.
Overall, I would still recommend this movie despite its shortcomings. Potentially this could have appealed to a wider audience and quite possibly have deserved to be Mexico's official entrant to the Oscar's best Foreign Film category.