I think that the main story of Aoi Spice is a very solid 6 but I enjoyed the side stories (well, 2/3) enough to bump the overall rating up to a 7.
There are plenty of other works that does the shoujo romance plot with more nuance, but Aoi Spice is short, sweet, and everything it needs to be. Though simple and straightforward it does not overstay its welcome by skipping quite a bit of the drama you may find in most shoujo manga.
If you are interested in the handcuffed plot point then know that it does not last very long and feels a little
contrived. Afterwards, the relationship develops in a comparatively natural direction, which is why I read through to the end.
If you like simple romances and you stumble on Aoi Spice then you may as well read this one. If your cultured tastes require depth and complexity, read other manga.