"From the 'truth is stranger than fiction' file comes this documentary about three New York artists (Henry Joost, Ariel Schulman, and Schulman's brother Nev) who learn that the Michigan family they've been corresponding with may not be who they say they are," begins Noel Murray at the AV Club. "Catfish unfolds more or less as it happens, day-by-day and scene-by-scene - all linked together by Google Maps animation and YouTube clips and GPS instructions and IM exchanges and other reminders that we're living in a world at once more connected and more disconnected than ever.... Catfish is absolutely riveting."

And it "delivers the definitive narrative of social networking gone awry to cap off the decade," writes Eric Kohn at indieWIRE. "By turns hilarious, unsettling and sad, the documentary engages with the rampant instability of new media.... It's purely a Zeitgeist experience: Using cheap digital cameras, the directors seemingly record everything, while Nev remains virtually wired to the online realm - and noticeably shaken when it betrays him."

Tim Swanson for the Los Angeles Times: "Most people in the audience shaking snow off their shoes probably circled the screening on their program because of the film's pedigree - it was produced by Andrew Jarecki, who directed the quicksand of a documentary Capturing the Friedmans, which premiered at Sundance in 2003. Those in attendance quickly found themselves enthralled by Catfish's veil-dance story - at first a detective tale, then evolving into a revealing personal journey - of friendship and courtship in the Facebook age."

It's "a sort of sad, unusual love story," but that's all I'll quote from Alison Willmore's review at IFC review, terrific as it is; she admits herself that she's probably telling you more there than you'll want to know walking in.

"A Sundance sensation, if Catfish isn't snapped up by some canny theatrical, TV or Internet bidder by the time I wake up later today, or is it tomorrow, I'll turn in my press pass," vows Ella Taylor at NPR. That was last night; evidently, as of this writing, HBO and others are circling.

For Filmmaker, Alicia Van Couvering interviews Henry Joost and Ariel Schulman; AJ Schnack gathers a bit more linkage.

Update, 1/27: More from Margorie Baumgarten (Austin Chronicle), Patrick Goldstein (Los Angeles Times) and John Lichman (Current Movies).

Updates, 2/9: "Catfish is fascinating for what it uncovers about identity games in the internet age and it eventually settles in to contemplate a situation both bizarre and deeply moving, but I couldn't shake the sense that the three filmmakers were more shallow than their own film," writes the Boston Globe's Ty Burr. "The midsection, as they chase down the  truth, reveals a casual youthful cruelty I don't think they copped to in themselves, and the last act wades into deeper waters than seem prepared for."

Eric Kohn talks with the film's makers for the Wrap.

Coverage of the coverage: Sundance 2010. For news and tips throughout the day every day, follow @theauteursdaily (RSS).