What a nice way to end the series and maybe the franchise in a way. This might be the last OVA was made for Sakura Taisen and the reason it was made was mostly for the voice actress of one of the main character, Sumire, as she was retiring from the Anime voice industry Michie Tomizawa (but later come back to the industry which is funny but hey, she voice Roberta for Black Lagoon so, no complain).
I can't say much about this OVA as it's just a farewell musical for Sumire so, they isn't much development for other character except for her when she realize it's time for her to step down from the Flower Division as she didn't have the power to continue to fight. It's a nice send off but other than that, they isn't much to say. Overall, a decent end for one of the character.
As for the franchise by itself, as someone who never play the game and going into it, I will say I have a mix feeling. For some like the TV series and the 1st OVA, it was good enough to like but for the other, it's was either average to don't watch it feel for me. I guess if you have play the game, almost all of them are very good for you and I can see that based on how they set up the OVA but trying to get people to get into this franchise will be difficult of how they set the anime up. I guess the best way to get into it is go watch the TV series and maybe stop there once you finish as after the TV show (exclude the 1st OVA), it start to get harder to follow. If you like the anime and want to know more of the franchise, I would recommend to look into the game as that is where this franchise shine the best. Unfortunately, almost all of the game are Japanese (except for one (the fifth edition?) that release in North America for the Ps2 and Wii). Still, they is fan dedication of the franchise like this link on
GAF where people talk about the game or walk through. Also, the gamefaqs have a detail walkthrough of the games which will help you if you decide to start playing the game.
Overall, I still have a mix feeling with this franchise but I will say it was fun to watch the TV series and make me have some interested in the game and want to walk some walk through for it.