One of the biggest challenges with using Ubuntu on a MacBook is getting used to all the "fun features" offered by the Synaptics touchpad, especially if you have big, clumsy hands like I do.
For instance, by tapping two fingers on my touchpad with a blank desktop, I can create a folder named "Untitled Folder". I'm not sure why I would want that, but it's definitely convenient! The problem is that a two finger tap opens up the context menu, and another tap selects the first item in the menu--which is to create a new folder named "Untitled Folder".
Another fun feature is that when I accidentally brush the touchpad with my palm, it'll find the virtual desktop where my browser is running and start scrolling the window. If I try to brush the touchpad in the opposite direction to get back to where I was, it just scrolls the browser in the opposite direction. That's because a two-finger drag on a blank desktop starts flipping through all the virtual desktops. Once you stumble upon a virtual desktop that has a fully maximized application, such as a browser, the two-finger drag just scrolls that window. You can't use the touchpad to get back to the original virtual desktop if there's a maximized window in the way.
As a Vim user, I was pleasantly surprised to find that my touchpad was helpful when using Vim. It's called the "I'm feeling lucky!" feature. Vim has two modes, insert mode and command mode. If you're in command mode and accidentally hit your palm on the touchpad, it'll paste whatever you have in X11's copy-paste buffer into Vim which treats it as random commands. It's even more fun in Vi since Vi doesn't have unlimited undo.
Last of all, my favorite feature is that "I'm feeling lucky!" works with the shell too. If you've highlighted a big block of text, and then accidentally hit your palm on the touchpad while typing in a terminal window, it'll paste all the things you've highlighted and treat them as shell commands. I think that feature is a useful reminder that you should never highlight anything with "rm" in it!