See, I still really like Family Guy. It's basically just a slew of cheap, horrifically unethical laughs, strung together fairly loosely by a weak plot, with characters who cross the event horizon every five minutes. Maybe it's 'cause I didn't follow it from the start, but I see that basically every time I see a Family Guy episode, and it completely appeals to my inner pre-teen and makes me laugh like a dick for 20 minutes. Actually, I find the earlier ones slightly less funny, if anything.
But Futurama... it's my favourite 'cause it's cleverer than all that. Hopefully that last episode was a blip. They've earned a lot of goodwill, it's the cleverest animated comedy on the box, and it's actually got a fair bit of heart, too. I'll be waiting with baited breath, but I reckon it'll be the exception rather than the rule. Fingers crossed. Heck, the boil crapshoot of a plot point was the exception even in the context of that episode, which was a bit too "new-simpsons" on the nose but still really funny. Enjoyed the previous two, too.
My guess is that it's just finding its feet again. I figure stuff's been shaken up a little bit what with the move to Comedy Central and the lack of regular normal-length episodes in x number of years, so they're probably a bit rusty. And probably trying to experiment a little, too.