You can't tell what the favicon is on a non-retina screen nearly as easily as other comparable favicons. On most screens, it looks like a small red dot at a comfortable reading distance. For example, compare the screenshot size of the identifying features of the new favicon to other random sites. (Chrome, but it appears in Chrome Mobile and FireFox as well):
You can't easily tell that the EE.SE icon is a diode, and that's not just because you have limited pixels.
- A 1.5-pixel perimeter is "wasted" to show the "leads" further away. This is not as important as being able to identify what the symbol is.
- The anti-aliasing causes an indistinct image in the center.
- The odd rotation results in higher amounts of destructive anti-aliasing (regardless of opinions on the rotation).
- The triangle and perpendicular line are the key identifying elements, and these need to be emphasized better.
I would recommend reducing the border given to the circle to the point that the circle fills the favicon more (or even completely). The leads are not necessary in such a small icon, and removing them may help with clarity. The triangle can be filled-in with white, if that helps. The actual lines should be larger than they are now, but scaling the whole image may be enough.
As an aside, please note that these are schematic symbols that are specifically and internationally recognized. There are very few ways to draw a diode correctly (1). It's like making a STOP sign with a pentagon instead of an octagon. This is why people are complaining when you take artistic license with the symbol.
(1): For the pedantic EE's in the crowd, I'm talking about a standard diode, not anything fancy. Yes, I know there are other types of diodes, and they are drawn differently.