Greta Gerwig Interview

The review from Variety makes her seem like an acting ninja; both present and absent at the same time:

Familiar until now only to fans of ultra-low-budgeters such as "Hannah Takes the Stairs" and "Baghead," Gerwig here makes her move toward the mainstream with work likely to divide, or at least puzzle, viewers. A big young woman who's attractive enough but not at all in the usual glamorous-actress mode, she offers no perceptible performance in the popularly received sense; you don't detect impulse, calculation, yearning, hidden feelings or anything else beneath the surface. She just seems completely real, behaving the way people do, just reacting to things as they happen. Either she's a total natural -- most likely -- or she has the most invisible technique of any modern actor. Either way, interest will surround her subsequent work.

And an interesting review by cinema blogger Glenn Kenny:

Ben Stiller deserves full acknowledgement as Greenberg's co-creator. His performance is some kind of career peak, a beautifully modulated piece of craft and one of the best bits of physical acting you're likely to see in a film for a while. Greenberg's whippet-thinness comes off as born of a certain kind of spite; Stiller's here highly-prominent Adam's Apple sometimes functions as a character in and of itself. Stiller's smallness of frame works wonders when his Greenberg, feeling defeated before he's even made an effort at accomplishing anything, curls up in a corner. Florence, Greenberg's romantic foil, such as she is, has a frame that's the opposite number of Greenberg's matchstick; obtrusive and awkward and gangly and hardly smoothed-out. Todd McCarthy got a bit of smack from some overly sensitive observers for referring to Florence's portrayer, Greta Gerwig, as "a big young woman;" but here she's supposed to be "big," at least relative to Stiller, and apparently she put on 15 pounds for the role.

Gerwig is, I'm happy to say, also very fine here. I've always found her to be an appealing screen presence, but this is really the first time she's been asked to embody a fully conceived character rather than present a haphazard compilation of tics, traits and attitudes. She acquits herself quite beautifully. Florence, who's the personal assistant to Greenberg's very successful brother, at whose L.A. home Greenberg is sojourning after a stint in a mental institution, is established right off the bat as almost shockingly passive, making her the unfortunately perfect receptacle for Greenberg's abuse and deflected self-loathing.