I have an expression and a silhouette cameo. And I like the cameo so much more. You can create images, alter existing images, weld your letters together. There are beautiful flourishes that you can alter and weld, also great full page cuts.
No books or carts to keep track of either, you just type in a search box and that will pull any image in your library related to that keyword.
Downloading images is really very easy, like Betsye said they download to the software. You can also download fonts from websites and use them with your machine. When you initially hook up a silhouette, any font that is on your computer automatically shows up in the program. And there are tons of great sites to get free fonts to download.