Poorly rounded UI corners

[aluminum313]

This one's kind of odd. I'm not sure if it's always been this way or I've just noticed. Running Safari 6.0.5 on OS X 10.8.4 on a 15'' retina MacBook, the bottom two corners look like this:

Very jagged, especially for retina. And yes, I'm running at the "best for retina" screen resolution.

The others mostly appear normal -- but Finder does something stranger. It's jagged in its regular state but when scrolled down down all the way it will appear smooth.

then

 

[yliu]

This scrollbar also look weird to me...

 

[sonicrobby]

Hehe, you guys are very meticulous. I havent noticed anything until you pointed them out, Im going to check on my rMBP when I get home to see for myself.

 

[redditMBP]

I noticed this today as well, posted it on reddit then found this after googling a bit more.

I filed this as a bug report with apple and included this screenshot:
http://i.imgur.com/ijheh2A.jpg

Those are some strange things going on.
Here's the bug report text:

Summary:
The lower corners of an application window that has a view which has any king of scrolling behaviour and fills the window left to right to bottom, will have the lower corners rendered in a jagged fashion instead of the smooth look the upper corners of said application has.

Steps to Reproduce:
On a new user, or any user, open up a Safari window and go to a web page, or use Finder and browse to the Applications folder with icon view enabled.
Compare the lower rounded corners of the application window to the upper corners.

Expected Results:
The lower corners of the application window should have the same smooth rounding as the upper corners of said application. TextEdit has the correct behaviour.

Actual Results:
The lower corners look jagged and are not smooth as the upper corners. In Finder there's an additional bug where ther seems to be an overlay of white running along the entire left edge of the Finder window.

Regression:
I don't know what this means, but this behaviour does not go away if I create a new user or anything like that.

Notes:
This is tested on a top-spec 15-inch retina MacBook Pro using the default retina resolution 1440x900. Switching video graphics from integrated to discrete does not change the behaviour.