So far, the only difference between the old and the new Apple TV is size and price. The new Apple TV is really tiny and still has a built in power supply (!) and at 99 USD it is a very affordable device.
For now, it is only for sale in the US. Does it work in Europe? Yes, it works well with 220V and 50Hz and a European flatscreen TV.
Is there any point in using it in Europe? No, not really.
If you live in the US and have a US iTunes account or a Netflix account, then you can use the Apple TV to rent movies and TV shows. It's quick, easy and fairly cheap and the image quality is good.