My iMac has an 3,1GHz Intel Core i5 with 16GB ... running eyetv 3.6.9 (7514).
It's definitly the software which makes the video stutter!
I've recorded some videos (1,5 hours), converted the mpg-file in the eyetv-archive with iFFmeg to AppleTV (mp4), and the video plays fluently!
So please keep an eye to eyeTV!
Michael