So, the local Samsung store has the S6 and Edge on display. Had a short look at it.
It's the best looking and built device Sasmsung has ever made. I cannot describe how many orders of magnitude this device is above the S5 in terms of in hand feel, material design and overall build. It definitely competes with the iPhone 6, and I think may surpass it in terms of material feel. The Edge in particular, has a very noticeable and solid "edge" along the sides.
The screen is absolutely gorgeous, and blows everything else out of the water with ease. It has a similar level of "floatiness" to the iPhones. Clear, tack-sharp, and responsive.
The software... well, it's TouchWiz. But, it melds with Material Design far better than I would have imagined. The iconography has been updated, it's far less garish and in your face. Overall, a decent improvement, but I'd still perfer stock Android as the overlay.
I can certainly see this device pinching sales from Apple. It's immensely well put together, and looks outstanding.