When you compare like for like , say an APS body with fast standard zoom compared to an APS mirrorless body with a fast standard zoom .There are savings in both size and especially weight the NX1 + f/2.2-2.8 16-50 has a total weight of 1232g the D7100 with the 17-55mm F/2.8 has a total weight of 1520g that is a saving over 20% :
Mirrorless cameras bring other advantages over typical DSLR’s. Compared to the D7100 ,the NX1 has a reasonable list of features that the D7100 lacks . Some more useful than others, they include focus peaking, 4K video , touchscreen , tilting LCD, higher MP sensor, 15fps burst shooting and so on.

EM1, GH4, NX1 and D7100 with their respective lenses
To put things in perspective.
The EM1 with 12-35 weighs 800 gr
GH4 with 12-35..................865 gr
NX1 with 16-50..................1232 gr.
D7100 with 17-55 Sigma......1332 gr.
See the difference. 65% between EM1 and d7100 and 7% between NX1 and D7100.
The 50-150 Samsung fares a lot better though and better than I expected when compared to the D7100 and its lens. But....
GH4 + 12-35 and 35-100 = 1235 gr.
NX1 + 16-50 and 50-150 = 610 + 622 + 915 = 2247 gr.
NX1 has an advantage here in FL too, spanning 24-225 vs 24-200 mm.
Now size of those lenses btw:
- 12-35 + 35-100 = 6262 cm3
- 16-50 + 50-150 = 1290 cm3
That is twice the size. so it is not only the weight but also the size.The bodies are far more similar btw, so it is really like most have said all the time. The difference is in the lenses. The only difference is the DOF. But that is not a one way advantage to either of both. If you want more DOF in low light, the m43 is at an advantage. If you want to single out subjects, it is the other way around. But the size and weight difference is svery significant.
When you do the same comparison between the Samsung and the D7100 and its lenses you are not coming close to such differences (of course). But the 50-150 IS significantly lighter in weight than the 50-150 f2.8 nevertheless.
I simply think that the name Samsung and a couple of nice specs, even when they do deliver in reallife, is not attractive enough currently. Not too much advantage to attract lots of Nikon/Canon/Sony users and way too heavy to atract m43 users. I think what Samsung has in mind and what will work, is the long run. Make a next gen of this cam and make it equally well etc and they start to gain traction. This is the first model to do so I think. And the main target first will be Canon then Nikon.