Overall, they are not flaws. They are design choices.
f/3.5 is not an issue for macro photography. Normally you would have to stop down to get usable depth of field. A big reason most SLR macro lenses are f/2.8 is to allow the phase AF to keep working at full magnification. Contrast AF of NEX doesn't have the same limit and can work at higher effective apertures. If f/3.5 makes the lens smaller or cheaper, I think that is a positive.
As for the angle, it may not be to everyone's tastes, nor suit every situation, but it still is a macro. I want a wide angle macro myself for the different perspective it offers compared to longer focal length macro lenses. It doesn't replace them wholesale, but supplements them. A shorter focal length at this time means the lens can be smaller. I'd guess longer ones will appear in time.
_________________Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.