@sakuchu He is too pushed over in my opinion. I can see him and Aria pretty compatible in normal circumstances a.k.a. regular folks like us, no money, power, survival of the fittest involved. But here, he is too dominated by his sister Iris. And from my personal experience (I am aware it's fictional and all), when you have to pick a side, you freaking pick a side.
At the same time, I do see that opposite attracts, Oscar and Aria can balance out each other: she is forward, brazen and cunning while Oscar is more reserved, follower-type and frankly naive. Which then put them in two further extremes - and extremes are too far apart.
Why Aria and Asher work out thus far although they can be pretty similar in traits (but do have differences, just that they are driven for different goals and purposes yet somehow were led to one another and aligned for the better and achievements of those separate ends) is that they really accommodate, have patience and communicate with each other pretty smoothly so far. Plus, they seem pretty clear headed with their feelings about one another and how they see each other as the only romantic candidate.
But, the authors haven't thrown around other side romantic rivals to mess thing up purposely yet. I don't know if they will appear... stupidly somewhere to stir up drama (this type of cliche is evidential in so many reincarnation mangas I assume that you also read into the genre). When this happens, it just drags the storyline and dumbs down the initial good characters.
I don't consider this as one of the best shoujos, but I still place it ahead of many others in the genre. I like how things play out, the lead character and the romantic partner being pretty clear-headed. I can name a few other with some similarities: Beware of the Villainess (pretty self-aware), A Capable Maid (like really feminine, breeze kind of shoujo), May I please ask you just one last thing, and This Girl is a little Wild (which sadly got discontinued ;_; was my first serious following too). They are all on the same tier with The Villainess Reverses the Hourglass.