Compared to a D80? I wouldn't say so.
The 5D's AF is not the best, and to be honest it is the main reason I plan to upgrade to a Nikon D600/D700 later this year.
However, the D80's AF isn't anything special, either. 11 points, 1 cross point in the center. The 5D I/II have 9 point AF systems with 1 cross point in the center, and also 6 additional "invisible" assist points that come active during AI servo. AF is certainly comparable between the two. In terms of speed, both will do 3 FPS continuous shooting.
The 5D will offer more than just better image quality compared to a D80. One other big difference is how much larger the viewfinder on the 5D is compared to an APS-C camera like the D80. I have a hard time using APS-C cameras after being spoiled by the huge viewfinder of my 5D.