Personally, there is an optimum weight to a camera/size. The added weight tends to remove shake at lower shutter speeds. Light weight is desirable in the body, and I think that is one of the reasons that mirrorless is so popular. If I can save a few hundred grams, that is an additional lens in the bag etc...
We can add weight later in the form of Zeiss/Leica lenses or battery packs. I found that the Fuji lenses felt very light for their size, it will remain to be seen how robust they are. ONe thing that I like about the NEX7, is that it has a very robust/dense feel to it, It feels solid and reliable, but this is just a feeling. It is too early to tell if it is based upon fact.
The one appealing thing about the lens is the speed and thus potential to throw more of the background out of focus for subjects *really* close to the lens - such as the shell cleaning shot. Unfortunately the OOF areas have some pretty ugly looking rendering along the straight lines of the crates. Edit: Just noticed they also have specified a much closer minimum focus distance (18cm vs 50cm for my ZM18) which ultimately will make more of a difference.
From some of the links in other threads, I have seen decent 18mm images and am not quite as put off by it. That said, I don't expect it to be a strong performer from corner to corner. What annoyed me with many of the lenstip samples was that the 18 was frequently misfocused and that many of the images, regardless of lens used, had a waxy feel to them...
