I worked in the US three years ago for several months and upgraded my rented Nissan Altima (not a bad tin box) to an Infiniti G35. It was a lovely, effortless, fast drive and as close as you could get to a four-door four-seat 350Z (which it kind of was) but the interior fit and finish wasn't much better than the Nissan, the bumpers were salad-spinner flimsy, the front number plate kept falling off and after three months of enjoyable driving the autoshifter came off in my hand after a possibly over-zealous slide into PARK. It was replaced in turn with a Volvo S60, a bit dull, reliable, white before it was fashionable, and not much fun at all, but solid. So, I'd say the G35 sat alongside a 3-series the way a 350Z sits alongside a Z4 or an SLK - go there if you don't want to be one of the crowd and you don't mind sacrificing quality for a different kind of laugh behind the wheel.
One more thing. Over there Infiniti rivals Acura, Honda's upscale brand. Over here they market Acura as Honda (our Accord being their Acura TSX) and don't even sell the Hondas they call Honda, other than down at Civic & Jazz level. Read into that what you like. What I read is that over here we expect better and won't be fooled by posh badges on bog-standard cars (unless they say A3 or TT.)
