A neat feature in Yosemite that I haven’t seen mentioned much is the new Preview pane in the Finder. If you display this, you’ll see a preview of whatever item you’ve selected in a Finder window. (This is new in icon view; it has existed for years in column view.)
Here’s an example:
I’ve got three files in the folder above, and I’ve displayed the Finder preview pane by pressing Command-Shift-P, or choosing View > Show Preview. I selected a file, and you can see a preview of it; in this case, it’s an audio file, and you can see its artwork, size, duration, date information and more. If you hover the cursor over it, you’ll see a play button; you can play the music. If you have certain types of text files, you’ll see forward and back buttons, and you can view their content.
You can change the size of the preview pane, but not by much. And it doesn’t play well if you use a colored background; by default, I have all my Finder windows set to use a blue background, and it looks a bit odd when the preview pane is visible, as there’s no visible separator between the two sections.
But this is a useful feature, one you may not want to leave on all the time, but one that you’ll toggle when you want to glance at different items in a folder without selecting them and pressing Command-I. It doesn’t display as much information, but what it does show might be enough.