Well it's larger than a 550D and nearer a 5D2. It's quite difficult to judge. Looking through the 550D feels like looking through a tunnel compared to the Fuji. The Fuji does make its viewfinder feel bigger than it "really" is because you can see around the edges of the frame lines. I like the superimposed histogram (and my wife will love the spirit level function) and it does clever things like after taking the shot, the EVF activates to show the picture, then zooms in on the focus point area so you can instantly judge sharpness.
ISO 3200 is looking good, though I hardly need to use it here in the house (had to turn out all lights but one bulb in the room, then getting ISO 3200 f/2 at roughly 1/40s.
The on-board flash balances itself beautifully with the background lighting. The on-board red-eye reduction is impressively accurate.