As the owner of 4th and 5th generation iPod touches, I've noticed that the 5th generation has far better reception (and therefore speed in some cases). The 4th gen used to lose connection a few hundred meters away from a building with a router, but its sucessor has full bars in the same places.
I've also noticed Bluetooth never skips while the device is in my pocket or behind something, which beats the 4th gen.