Lighter yes, but not compacter enough to make a practical difference for my applications when I am doing serious photography. You will need a bag anyway to carry both systems since you will need more than one lens when doing serious photography, or should I say "I will need more than one lens".
For me its a real downsizing of my bag. I really only need one to two lenses for most of my photography, a 35 and an 85ish. It's absolutely perfect coincidence that Sony made the just right choices for me with the crop-sensor 24 and 50. Apart from that I will need a telezoom – I don't know if the new 55-210 will be of sufficient quality for my needs. And one tele macro such as the Sigma 105 or 150 OS. So when I carry around the macro lens as well (including the AF adapter) it won't be so much less weight as with a DSLR setup. Absolutely right!
But if I don't need the macro, which is the case for a lot of my traveling photography, it will just be:
291g => body
60g => battery
225g => 24
200g => 50
350g => 55-210
This whole bunch is only 1.13 kilogram. This is even less than my actual DSLR body alone weighs. Also it will fit in my smallest Crumpler bag.
In the very, very few cases that I want to go "wide" – it's really not a serious part of my photography – I just might buy the so-so, but cheap and tiny 16 pancake lens. I would never have a similar small option on any DSLR. Generally, I am absolutely not
into super-wide-angle photography, even for landscapes – which might be different for a lot of you folks. But I can't speak for you, just for myself, obviously. Also I do know that DSLR are also about fast focusing, action photography and the like. Yes. But I never bought them for these reasons cause that's not what I needed them for. Again only speaking of myself.
Probably it makes more sense to think of the NEX as a rangefinder system with added tele and macro capability. And no one would argue that the classic rangefinder systems appeal to some photogs, for very good reason.
Now I am not doing serious photography all the time but when I am not I want a high quality version of my iPhone experience, click and get a sharp image whatever the subject and conditions.
My personal "serious photography" is about rather still subjects, travel, cityscape, details and landscape, and printing these at sizes up to 20x30" (rarely a bit more). Apart from that, I am very dedicated to macro photography (insects of all kinds). It might be that your serious photography is much different to this and that you will demand much different cameras than a NEX-7. Absolutely understandable.
For a high quality version of an iPhone photo experience, I recently bought a NEX-5 which is even smaller than the NEX-7, with heavy compromise on the UI, but still really astonishing file quality. I might just pair that with the upcoming 30/3.5 Macro lens. Or with the 24 or 50, just according to my mood. It won't fit into any of my clothes' pockets, but I usually always have a small bag with me for all my belongings and stuff, and that still rather little camera won't eat much place in there, and also does not cost so much that I have to really worry about it going with me almost everywhere. A Nikon 1 would need just as much place, cost at least just as much, and offer inferior image quality in every respect, for example.