Critical in a curmudgeonly sort of way.
The adjective snarky is first recorded in 1906. It is from dialectal British snark, meaning 'to nag, find fault with', which is probably the same word as snark, snork, meaning 'to snort, snore'. (The likely connection is the derisive snorting sound of someone who is always finding fault.) Most dictionaries label snarky as "Chiefly British Slang." But for the last five or more years, it has become increasingly common in American publications, maybe ones infiltrated by British or Canadian writers and journalists.
Anthony Lane is the current champ of the snarky film review.