"Side tracked from its original story and ended up being a half-baked series."
Before we begin, let me drill this into your mind. Fan service; Fan service; Fan service; Fan service; Fan service! That's the theme for this anime so don't start having high hopes for an amazing story or what not (at least nothing in comparison to the manga original). Rosario + Vampire, like many manga-to-anime adaptation series, made fans screamed with joy at first, but only to have their hopes and dreams shattered bit by bit as the anime progresses. It is true that the anime's story plot deviates from its origin, but it is also true that the artwork is astounding (the animation version of the characters look more attractive to me). So let us get into a deeper analysis of Rosario + Vampire.
The anime is considered pretty episodic (ie. standalone episodes) with a few exceptions near the end of the series. This goes parallel with its manga originals so it is nothing new to the readers. However, what is new is the extremely formulaic sequence in all episodes with an introduction to the "monster of the episode" (these monsters tend to get defeated and then become friends with the protagonists). Not only that, but the actual story coverage is also very minimal in the anime (only covered up to chapter 10 of the manga out of 40 chapters). But that is not to say it is all bad. In fact, certain portions of the story that were remade into anime were better planned (events flow smoother/made more logical sense) than the manga version. Overall, the story serve its purpose as an introduction to the Rosario + Vampire series.
Consistent animation quality throughout, beautifully animated characters, plus smooth transition from scene to scene, what more can you ask for? Gonzo, while not exactly known for extremely high quality animation (at least not at the level of KyotoAnimation), does indeed proved itself a worthy opponent to other studios in the industry.
OP and ED are both very enjoyable for me (I didn't skip them like I did for a lot of other anime). It should not be an annoyance to you either (I hope). As for seiyu, there are many talented and well known professionals to voice for our pretty girls (and boys). For instance, there is the cute Rie Kugimiya voicing for the "icy cold" Mizore, and Saeko Chiba voicing for the "very funny" Ruby.
I would like to bring the attention to Nana Mizuki who is the CV for our super hot/cute/pretty/gorgeous Moka and also the singer for the OP and ED of the series (and the singer for Capu2 as well). Nana is not only famous in the seiyu community, but is admired by all. She has an amazing ability to sing (even rivals those so-called "professional" singers) thanks to her powerful singing voice despite being a pretty tiny girl. She was also the winner of the “Best Musical Performance” award in the first Seiyu Awards. For those who have not yet experienced her excellent character voicing ability (and as a singer), I strongly suggest you give this series a try.
Aside from the fact that most character's hidden abilities were not included in the anime, the show did a pretty good job with the characters. Plenty of character developments and showing their inner feelings toward each other (especially near the end when certain secrets were discovered). In addition, the interaction between the many different types of monsters can be quite refreshing from the traditional harem-oriented anime.