For me, this movie brought in some interesting connections to the old cartoon series, including one major reveal that would only get old-school nerds such an myself excited: Unicron. Aside from that, I enjoyed the movie for its main draw: watching robots transform and fight. Some of the scenes were breathtakingly created. One could pause the screen at almost any point and have a shot worthy of being put on a poster.
This movie also brought in Arthurian legend (albeit corrupted) which is yet another series of stories that has yet to reach their theatrical potential (sorry, Excalibur fans, but the first two seasons of the BBC Merlin were really the closest to capture the true spirit of the legend). Of course, this Transformers movie retconned its origin story (yet again) to fit the Arthur story in and then did not fully develop it as it bumbled its way through the web of plots that it tried to develop. Trying to follow the twists and turns of this series is like trying to make sense of the Pirates of Caribbean sequels. Like those movies, I keep hoping for something better in the next film.
Despite Michael Bay's protestations that this is his last Transformers movie (a claim he's made after every sequel), this movie clearly sets up the next in the series. While it will no doubt fall short of expectations, the boys and I will probably watch, and enjoy watching, that one as well. However, I doubt I will ever run a marathon viewing of the series. There is only so much that I take in a single sitting.