I just found out that the --filter option has been removed from bsondump
It would've been nice BTW if the documentation mentioned at least a reason for this change:

http://docs.mongodb.org/manual/reference/program/bsondump/

Nevertheless, I'd consider this a regression. It's so much slower to dump and grep in huge files. In addition there seems to be no progress output anymore no matter whether I specify -v -vv or -vvv which makes restoring a single record from a dump under 3.0 nothing for the impatient...

Please consider adding the feature back again. It was extremely useful! I'm using the binary from old Mongo versions which I copied over for now...