Seibertron received advance copies of the first two episodes of Transformers: Prime and decided to write up spoiler rich summaries of each with lots of screenshots. "Darkness Rising" is the name of the first five episodes of the series as it lays out the characters and circumstance of this new cartoon series. These first two parts premiere on Friday at 4pm EST (repeat at 6PM EST) on The Hub with the remaining three airing the next week. The confusing schedule can be found here. Still not entirely clear what day and time the show will start airing on a regular basis after that as The Hub PR department is doing an awful job on making schedule info available.
Update: Variety posted a review of the cartoon. In short, they liked it, saying the cartoon "proves unexpectedly sharp -- better than the movies (admittedly damnation with faint praise), thanks to the arresting CGI animation, which proves especially well-suited to rendering shiny robots and their vehicular alter egos." Full review here.
Based on the description, the series starts off with a bang with a death, call to arms, and Decepticons on the move. If you don't mind the spoilers the summary of Darkness Rising part 1 is here and part 2 is here. Thanks to Christopher for the link.