Many swear by the Israeli Galil:
http://remtek.com/arms/imi/galil/galil.htm
http://world.guns.ru/assault/as23-e.htm
It comes in 7.62mm x 51 (NATO) or .308 caliber. The above link will give you a good history.
If the Israelis like it, then you can bet it's a good design. If their forces are armed with it, then you can bet it's combat proven.
I've never used it, but I have used the M-16A3 (5.56mm x 45 NATO). It's a solid rifle and I highly recommend it. If I were going to get a rifle in a .308, then I'd look at the Galil.