In praise of the UWA 0.75 adapter
I have it too and am looking forward to using it in my Europe trip in July. Hopefully it will keep me off the Touit 12mm.
Touit is way better glass, no doubt about it, but myself I can't afford almost 5x more expensive lens (got my used SEL16 for ~$150 + new UWA for ~$100). And if I could spend that amount I would do the SEL 10-18.
One small advantage of this combo is that you actually have two lenses
Not the best example below, as it's shot at ISO400 but you can do some pixel-peeping (almost original size, edited in LR4):