It lives in your menu bar where, when clicked, it’ll open a drag and drop window. You can also access it straight from your keyboard by hitting ⌘+Shift+8. From there you can throw in multiple images of differing file types and select whether you’d like to convert them into JPG or PNG files, or merge the photos into a single PDF… More at lifehacker.
Looks like a decent choice. This is a task that I have battled with for a long time so the more options the better in my view.