Jeff: I thought i could do it somewhere - must be an old oracle memory!
The old postgres set autocommit to 'off' would have had the same effect - i really don't care about rollback ability, i just don't want to fsync on every insert since i'll be doing ~8000 of them!
Of course I could manually check all the constraints on the input data and filter those rows out first, but this way is so elegant, an ensures there is no mismatch between the way you enforce your business rules.
The sync options I came up with above are still significantly slower than inside a transaction, so i'm still very open to ideas. In fact sometimes it doesn't speed things up much at all - i suspect the MORE loaded the database the less fsyncs will occur in this case.
