I am a long-time Family Guy devotee, I own all the series on official DVDs and have watched them many, many times. I pretty much can't go to sleep without hearing the theme tune on BBC3!
This series continues in the same vein as all the others, with the same solid animation style, close-to-the-bone humour and random flashbacks. I would say the writing isn't as strong as in series 4 and 5, but there have always been a few dud episodes in every series so this probably isn't anything unusual. There also seems to be a lot more swearing in this series too, though there is still considerably less than in other adult shows like True Blood, The Sopranos, Misfits etc. That really is something to remember - FAMILY GUY IS NOT FOR KIDS!
Really, there's no better accolade that I can give than to say if you are a fan, buy it!