Quite small already with the 20-50 kit lens, even more so with 20 or 30mm pancake lenses (like this it will easily fit in many coat pockets). Still larger than most compacts of course, but with a lot lot better controls and lenses.
Good sensor, but I get the impression this isn't the best camera for low-light use. For flash photography I can't comment.
Talking about lenses, there aren't a big range available. The 20 and 30mm pancakes are good, the 20-50mm also seems good. I've heard some of the shorter focal length ones aren't so good. The 50-200mm zoom is moderate, but not great quality at high zoom. It's heavier and much bigger than the camera body, but that shouldn't be surprising.
Fun to use. It has two dials on the body which makes it easy to change the most important settings. I do have a gripe though: manual focus can be done in two ways: zoomed in, or looking at the whole frame. Neither is perfect: the zoom takes the whole screen and makes framing difficult (especially because any touch of the focus ring will activate it), while the whole frame mode isn't always easy to get good focus. I'd prefer just the center of the screen to be zoomed in. Also, forget about the "i-function" thing on the lenses. In practice the dials on the body are always faster and easier to use (if you're holding the camera; tripod use might be a little different).
For the little things like batteries and memory cards I've had no problems. You can get a class 10 16GB card and a second (third party) battery very cheaply, which will certainly keep you going all day.
Summary: I like it and don't regret my purchase. It does seem compromise is necessary to have a highly-functional yet small camera, partly because it's a relatively new market and partly simply because of the size restrictions. Also note that you're not going to see a lot of high-zoom lenses in this category because when you've got a big lens there's less point in worrying about the size of the camera; small interchangable lens cameras are a good form factor but not a universal one.
Samsung NX200 KIT Compact System Camera: Fully-loaded compact system camera
Pros: Snappy AF performance in good light, New i-Function, Improved build quality and ergonomics, Good range of digital filters, Expanding range of available lenses, Good ISO noise performance, Good screen, Easy to use
Cons: Battery life, Occasional slight inaccuracies with WB and metering, Slower performance in low light and when shooting raw files, No viewfinder option, Delay after continuous shooting, White balance presets quite strong