It's either gonna suck or be okay.
Very insightful, Nostradamus.
I have no doubt the new show will be clever, because it comes from the same creative team. The real question is: how will FOX fuck it up?
To begin, the idea behind "American Dad" was to replace "Family Guy", not supplement it. Now the two shows are actually competing in some respects. As long as Fuzzy Door productions takes this into account, they might be able to successfully crossover the two shows at various points.
If the past is anything to go by, the downward spiral of both shows should proceed something like this:
FOX will air "American Dad" on Sundays following "The Simpsons" for its first few weeks. They'll follow that hour block with (ugh) "Quintuplets" or a couple of Malcom re-runs, especially after "Arrested Development" finishes its second season. They may even try to introduce a new shitty show immediately following "American Dad", especially if that schedule is maintained into the Fall.
"Family Guy" will be on Thursday, or possibly Tuesday. It will be supplemented by "That 70's Show", and will almost certainly be followed by yet another really, really shitty new FOX mid-season sitcom, probably about a Mexican family or an 80's comedian.
Within six months, both "Family Guy" and "American Dad" will have switched nights three times, will have been pre-empted by sports and Latin awards shows six times (each), and will be buried, reshuffled and lost by the network.
As a result, the ratings of both shows will droop, and they will be cancelled after one or two seasons. However, DVD sales will again skyrocket, and the fans will, once more, wag back and forth on the internet about how they are at a loss as to how FOX could be run by such a collection of clueless assholes.