While I was watching this anime, I couldn't help but compare it to another girls' love anime I watched once: suffice to say, it's one that it kept me away from the GL genre for a while for having too much fan service and too little plot. Well, as it turns out, Maria†Holic fits that description a lot better.
You'd think the plot would be centered around the cross-dresser Mariya and her reasons to do so. It's not. The moments in which this is developed in the plot are few and far in-between. In fact, the plot is basically non-existant: the whole series feels like a bunch of random scenarios thrown together.
The lack of plot makes most of the cast uninteresting, since there is no development whatsoever. Some are still good, though. There is the Dorm Mistress, who's pretty funny, there is Matsurika (Mariya's maid), who reinforces Mariya's personality pretty well, and finally, there is Mariya herself. Mariya evades the delicate crossdresser stereotype completely. She is just EVIL, something you have to watch and see.
As for the main character, well, she is a pervert. By fantasizing about whichever girl(s) is(are) on her vision range, she puts famous pervs, like Brock from Pokémon, to shame. She is, of course, the excuse for a whole truckload of fan service. If you are looking for anime girls in bikinis and bras, you just found them. Unfortunately, I wasn't.
Now, see, you might notice that all I did until now was to bash the anime, and yet I gave it a 7/10. That's because there is one very important point about Maria†Holic that needs to be made. This series is NOT supposed to be taken seriously. It doesn't take itself seriously, and you shouldn't either.
So what if the scenarios is completely random? It's still pretty funny. In fact, there are so many situations that are so absurd and completely blown out of proportion, you WILL want to continue watching it even after making the "wtf am I watching" face several times. It's those kinds of things you'll only see in an anime.
Finally, I'd like to comment on the opening and ending sequences. They are awesome.
In summary, my thoughts on Maria†Holic are basically this: Take it lightly. Don't come in expecting lots of romance and depth, instead, just expect goofy humor. You'll enjoy it.