Very intuitive, if you are an ex iPod Classic user, you'll pick it up pretty quickly. The bottom right and left buttons are for navigating songs forward and backward and fast forward/fast rewind. The center button is for selection and play pause plus volume display. The top right button is for screen backward action (one click get you one menu level backward, press and hold get you back to the main menu). The top left button is for shortcuts and main menu. It will take you literally few minutes to get the hang of it.
So if you have the X5 in your pocket, the bottom right and left buttons plus center buttons are the only ones you need to worry about.
Which button accesses the internet, and which one allows me to dial a pizza? (*with a bag of chips, sauce, and a beer)