well, 6.5.1 has many improvements in UI. It makes look of 6.5.1 beautiful. see attached screenshot.
But at the same time improved UI has bugs shown on another screenshot. Not all programs (including some from samsung) look correct with new thicker bottom bar and thinner upper bar.
IMHO, 6.5.1 is not ready for the masses yet.
I agree, but still, it's worth trying and way better than 6.5.1: it's the reason why I will sell my O2 when it comes back from servicing to buy a HTC HD2, the Blackstone successor. WM 6.5.1 works well on it, plus, the screen it's bigger, although not AMOLED