I personally find those plug in batteries to be a better solution, especially as you can use them to charge multiple devices.
Meh, I think the only ones you can get for micro-SD devices are the duracrap ones, no? Besides, the GS2 batteries (Anker 1900mAh) were £11 each. And trying to charge with solar, especially here, is not exactly feasible. It's colder here in May than it was in December and probably cloudier...
I think if youre going to make a large screen, 7"+ with a density of over 300ppi then pentile makes perfect sense for OLED. However on smaller screens i dont think it should be used, unless maybe youre pushing over 320ppi maybe. The cost saving going pentile on a 4" screen cant be that much, id imagine its nowhere near enough to justify using it on a flagship device.
I think that it should be used for small screen's with higher resolutions where the cons of PenTile or not visible or less visible.
I think the reason they didn't use a non PenTile screen is because there isn't a 4.8 inch 720p Non-PenTile screen yet and PenTile also works with about 20% less power.