This is a very interesting subject. At least for me, as it draws on two of my passions: HCI/UX/usability and, well, music.
I think this kind of approach is defined essentially by a closer mapping between the sheet and the physical world (which is, according to usability tenets, something good). So, under this "definition", we can consider other approaches which are very popular and indeed work: guitar tabs and "Guitar Hero"-like games.
In the wise words of Thom Yorke, "anyone can play guitar", and I think this is - nowadays - mostly due to guitar tabs. Tabs make it very easy to step into guitar playing. So, I think, it's not a surprise that these approaches are so popular, as they have a easier learning curve for beginners, which is in itself also not a surprise if we consider the usability principle of close mapping with the real world. Traditional music notation just has more layers of translation, so to speak.
So, what are the drawbacks of this? I can think of three, which might explain why these approaches aren't promptly adopted by traditional music education:
1) As this is, essentially, a closer mapping to the physical world, said mapping has to be "done" to a specific instrument. An alternative notation such as this one or guitar tabs wouldn't be very helpful for, e.g., wind instruments. So, with this we would create specific "languages". Arguably, having musicians understand an universal language is a good thing - I'm no piano player, but I can read a piano sheet;
2) Repertoire, generally. The amount of music written in traditional notation is just huge, the inertia to start writing stuff with a different notation would be a problem;
3) Dynamics: I think these approaches overlook dynamics. It's not only about what and how long you play, it also about how you play it. For wind instruments, e.g., the dynamics can get quite complex - if a pianist has to read 5 notes, a flute player has to read one but with 5 dynamics annotations. This is, however, somewhat addressed in guitar tabs, as there are quite excellent tabs with not only dynamics annotations but also instrument-specific techniques. Maybe, in this approach, circle sizing could be used to communicate velocity?
I think this kind of approach is defined essentially by a closer mapping between the sheet and the physical world (which is, according to usability tenets, something good). So, under this "definition", we can consider other approaches which are very popular and indeed work: guitar tabs and "Guitar Hero"-like games.
In the wise words of Thom Yorke, "anyone can play guitar", and I think this is - nowadays - mostly due to guitar tabs. Tabs make it very easy to step into guitar playing. So, I think, it's not a surprise that these approaches are so popular, as they have a easier learning curve for beginners, which is in itself also not a surprise if we consider the usability principle of close mapping with the real world. Traditional music notation just has more layers of translation, so to speak.
So, what are the drawbacks of this? I can think of three, which might explain why these approaches aren't promptly adopted by traditional music education:
1) As this is, essentially, a closer mapping to the physical world, said mapping has to be "done" to a specific instrument. An alternative notation such as this one or guitar tabs wouldn't be very helpful for, e.g., wind instruments. So, with this we would create specific "languages". Arguably, having musicians understand an universal language is a good thing - I'm no piano player, but I can read a piano sheet;
2) Repertoire, generally. The amount of music written in traditional notation is just huge, the inertia to start writing stuff with a different notation would be a problem;
3) Dynamics: I think these approaches overlook dynamics. It's not only about what and how long you play, it also about how you play it. For wind instruments, e.g., the dynamics can get quite complex - if a pianist has to read 5 notes, a flute player has to read one but with 5 dynamics annotations. This is, however, somewhat addressed in guitar tabs, as there are quite excellent tabs with not only dynamics annotations but also instrument-specific techniques. Maybe, in this approach, circle sizing could be used to communicate velocity?