iPhones all use PenTile and nobody complains about fuzzy text on them. Early generations of pentile weren't that great, but modern ones look fantastic at basically everything. See also everyone considers the iPad Pro to have probably the best display available at any price point - and it's not an RGB strip, either.
The PPI difference matters though (and I think why my Nokia N9's PenTile OLED looked rough). Desktop displays simply aren't at the same PPI/resolution density, which is why they're moving to this new technology.
If it didn't matter, I highly doubt they'd spend the huge money to develop it.
PenTile for example (as another commenter pointed out) was woeful with text, and made things look fuzzy.
I'm not a fan of ClearType, but even on Linux OLED text rendering just isn't as good in my experience (at normal desktop monitor DPI)
Perhaps its down to the algorithms most OSes use instead of just ClearType, but why hasn't it been solved by this point even outside Windows?