This is a feature that Apple's buttons don't have, and I think they look cool. If you didn't read the chrome tutorial , here's how to do this part. Create a new layer and select a huge fuzzy brush. Make sure your brushes are set up in incremental sizes first. Now add a dropshadow layer effect to the original black pill layer.
Water is transparent, so light shines through it.
Thus, your button shouldn't cast too dark a shadow. It should probably even be the same color as the button, although I think Apple uses a standard gray shadow. Add some black text to the button now. Mum's the word, but Apple uses Lucida Sans in Mac OS X. Frutiger Roman will do nicely, also. Probably the worst mistake you could make with this effect is to use a plain font like Helvetica or Times with it.