Zoom button

We know that the zoom button (top left silver curved button) can zoom a mat by holding the button and tapping on the area of the mat you want zoomed. (Recap: Hold the zoom button and tap on the spot in the mat you want zoomed. If you want more just keep holding the zoom button and tap some more. I think 3 times brings you to maximum. This maximum zoom is to the exact scale which you can use your ruler to measure - which is helpful while designing. Then to unzoom just hold the zoom button and release without tapping)
But some of the other functions (some works with only the newer updates) are

1. Scrolling through the lists. Note here: In 0155 you had to hold on to the button and make your selection while still holding on for if you let go the list went back - or atleast  my G behaved this way ;) - for with the G who knows. But this has been fixed in the later updates and again my G behaves this way now.LOL 
2. Zooming an image on the keypad overlay to full screen so you can see the image better (by pressing zoom and tapping on the image). But just now I found out that this feature also works in the keyword search that way. If you tap on the lower white box where the cartridge window is - you get the image and the cartridge it is from. Just press the zoom button and tap on the image (not the cartridge) and it will bring the full screen image so you can see better and then make a choice. To go back to the regular screen just tap on the screen or just press the zoom button and it will take you back to the previous screen. This works even on photo app to see your photos.