The first impression is very good. The metal is extremly hard and I have the feeling it would rather break than bend. Definitely what you want for this scale.
As you can see, these miniatures are superb! The amount of details is simply astonishing.
This thing is the size of a small Titan and stands up easily to a 28mm miniature:
Painting 6mm is quite different from what you do with 28mm miniatures, and because of the extreme zoom mistakes are more prominent in pictures.
Conclusion: The Onslaught Miniatures 6mm range is amazing. All the miniatures I got are of a very high quality and feature so much detail that painting them becomes even more challenging.
And to give you a small taste of what is coming in the future:
The Yamato Super Heavy Lander for teh OTC has just been announced and the first 15mm scale sets (based on the 6mm range) should be available very soon!