1anakin said : The hand that Obi-Wan cuts off, it looks to dead for just being cut off, it looks like rock.

That's Ady's hand, I'm not sure if he adjusted the colour to look like a dead limb but like the original actor and myself he is British and we don't get much of an opportunity to tan over here (perhaps it should look a bit tanned because of the desert planet setting but the character is an alien so maybe his species just doesn't tan).

The planet is a real one, possibly the only real one in any Star Wars film (it's a HD NASA photograph of Earth). That in itself would be no excuse if it didn't look good, I don't have a problem with it but I'm open to look at different varieties.

I personally don't have a problem with the red R2 Unit, maybe a little bit more variety in the markings could make it look even more like a different droid but it's possible you have seen the film so many times that you expect to see R2D2 there.