Having slept on this show for quite some time, I was surprised how good the first season was, and just after finishing that I went ahead of wolfed down season 2. Watching the two so close together, there were some bigger differences between the two seasons, but the common thread was the invention and hilarity of each episode was at the same high level. The use of other characters is extended, so that the family are not just caught up in Rick's world, but actively participate and seem at ease with the other worlds they are exposed to - this is a bit of a jump but the show carries it very well.
Another small change is that this season doesn't feel like it has a thru-line or a build. The season finale suggests otherwise, but mostly the season doesn't have a thread that stands in for the world building of the first season. This is understandable but it is an absence I felt in the season overall, even if no specific episode was lesser for it. The key thing is how funny so much of it is, and how smart a lot of the writing is. Adult Swim have signed on for another 70 episodes apparently, but I'll try to hold off a bit before watching the third season, lest I have the long waits of those who watched from the beginning.