I finally watched this on my 2010 Samsung 3D plasma yesterday. The 3D effect was very strong, very immersive with a really nice sense of depth and height, especially with the gears and machinery within the clocks. Panoramic shots of the Paris and the train station seemed to go on forever and closeups also had nice depth with articles of clothing like the stationmaster's hat seeming to protrude from the screen. Not too many popouts but the ones on display worked well such as the dog snarling right out of the camera or the pirates swinging their swords during the flashbacks of Melies creating his films.
Ghosting was pretty visible on my plasma and, as expected, it mostly revolved around scenes of extreme contrast ranges such as the shiny metal of the automaton against the dark background, Hugo's pale face against his dark hair, and Melies' while shirt against his black tux near the end. This has always been a tripping point for plasma 3D displays so I wasn't surprised to see it here. I also had a slight headache after watching the movie and that's something I typically don't experience with active shutter 3D. I'm having an LG 7600 passive TV delivered Thursday and I'll be curious to see how it holds up with that technology.
In spite of the ghosting issues, I do think Hugo marks the best use of 3D yet; it definitely serves the story and helps to pull you in. Considering the film is a celebration of one of the pioneers of creative filmmaking, the use of 3D seems even more appropriate.