Take a look at the portafilter. Is it made of plastic that will break quickly during everyday use or is it made of a sturdy metal? Also look at the portafilter handle and how it rests in the machine. How far over do you have to move it to lock it? Do you have to hold a clasp in place to keep the filter basket from falling out?
You'll also want to notice how much clearance there is between the spouts and drip tray. Will it fit the type of cup into which you want to brew? Speaking of cups, look at the cup warming tray. Does it have one? Is it usable or just for looks? If you are planning on making more than just espresso, like a cappuccino or latte, make sure your machine has a steam wand and a milk frother.
You'll also want to make sure to get the right kind of steaming pitcher. A common design is the "bell shaped" or round pitcher with a handle and no (or little) pointed spout. Unfortunately, this type of spout is not ideal for making impressive latte art, or even pouring decent cappuccinos and macchiatos without the aid of a spoon. Instead, you want a pitcher with a good pointed spout. When considering the size of your steaming pitcher, a 12oz pitcher is reasonable for making two macchiatos, one cappuccino or a small latte. A 16oz pitcher is good for making two cappuccinos and 20-24oz pitchers are best for making multiple cappuccinos or 1-2 medium or larger lattes.