IMHO a pressed active Button is too low in contrast and too flat looking when compared to an unpressed active one. As as result, it's hard to tell that such buttons are press-able, and which is the current pressed one from a set of options - in a radio or stack group for example. The button almost looks insensitive, which doesn't convey the notion that it's active/selected.

Here's an example from Nautilus:

http://i.imgur.com/6pFEiPV.png

The Home button is active unpressed, Pictures is active pressed, and the rightwards arrows are inactive. Yet the Pictures button is so flat and low in contrast that the user might reasonably (I hope for me...) assume it's inactive, or at least that it doesn't visually seem to be a selected button.

Of course, you want to convey that the button is pressed down. But I'm not sure making it so flat that it looks inactive is the way. Perhaps it should have the same amount of relief as the 'up' case, just in the 'down' direction! As of now, it's so flat that it doesn't seem like something a user can interact with.

And again, IMO it's not coloured strongly enough to indicate it's the pressed button, e.g. if it's next to others that might be unpressed, like those pics.

I would say that more relief and a more intense colour would better indicate that such a button is both press-able and currently pressed.

http://i.imgur.com/4y1DXeJ.png

This is the same pattern but for the other theme variant, just to confirm it applies there too.