If you've had any interest in an Xbox 360 (either as a gamer or a loved-one-of-a-gamer), you've probably heard about all the trouble they've been having. The machines have been failing due to internal heat build up, also commonly known as the "Red Ring of Death" due to the 3/4 circle of red lights that appear on the console when it dies. Several friends of mine have had this happen more than once.
Microsoft has worked very hard to address these issues. When my own Xbox gave up the ghost last month, I shipped it back and received my new one in less than a week. When these problems first started appearing, the wait time was closer to a month.
They have also redesigned the components inside the Xbox, and a new version (codenamed "Jasper") is out in stores now. It includes a chipset that consumes less power (therefore generating less heat) and onboard storage memory to accomodate the New Xbox Experience (NXE) dashboard software. But how can you know if the one you're buying is a Jasper? Just look through the hole on the box. The 12-volt side of the newer Xbox power bus required 14 amps. Jasper models require only 12 amps. The text visible through the hole will tell you what's inside.