This season is almost as good as the first. Lots of action, laughs, and even a couple of character study-type stories. The main threads of the season are Sari's search for her father, everyone hunting for pieces of the Allspark, and Megatron trying to complete a space bridge.
We get to meet the Elite Guard that was mentioned so many times in Season 1. The first three episodes introduce a large part of Optimus' past with the Guard, especially his interaction with Sentinal. And we get to see Jazz! An excellent trio of stories, especially where the Headmaster makes a return.
There's another episode where the Constructicons show up, one in which we see how Bumblebee and Bulkhead met (with a special appearance by a certain 'bot), another where Starscream is forever trying to defeat Megatron (with hilarious results), and an episode dedicated to Prowl and what he could have been if he had taken up Lockdown's offer. A later episode has the return of a G1 character, complete with the original voice, which will give any fan of the original cartoon a thrill.
And speaking of Prowl, this season is the first time we get to see him actually transform. If you were paying attention, the audience never got to see him with a transformation sequence in the first season. This season, we see it once.
My only issue: The plot of breaking the Allspark and hunting for the pieces with a specific person/object is almost an exact duplicate of the Inuyasha main storyline.
Overall, if you enjoyed Season 1, you'll definitely like Season 2. Two thumbs up!