Microsoft's Xbox team unveiled details of the system-on-a-chip (SoC) that powers the newer, slimmer Xbox 360 250GB model. Produced on IBM/GlobalFoundries 45nm process, it's fair to say that the new SoC is the "first mass-market, desktop-class processor to combine a CPU, GPU, memory, and I/O logic onto a single piece of silicon". The goal of the consolidation was, of course, to lower the cost of making the console by reducing the number of different chips needed for the system, shrinking the motherboard, and reducing the number of expensive fans and heatsinks.
The new SoC has only 372 million transistors, which is just not very many by today's standards. For reference, the old 65nm Pentium D 900 from 2006 has almost the exact same number (376 million), while the upcoming 45nm Core i5-760 has almost double the transistor count (774 million). So, despite the fact that the new SoC contains all the silicon brains of an Xbox 360, it's still very svelte by modern standards.