Like many have mentioned, this seems to add a lot of noise to notation. This isn't really demonstrated in the pieces they have on the site. I'd like to see what it looks like with something a bit more complex like a Bach Fugue. I feel like the rhythm notations, in particular, would become more difficult to parse as the rhythms become more complex.
Also, how do you notate tuplets?
(1) Hummingbird translates length in a trivially superior way to standard notation. No contest imho.
(2) I would say it does a somewhat better job on pitch as well. Both have huge shortcomings so I can well imagine far better systems.
Dynamics is a push so I'll say Hummingbird is an improvement in translation. I don't think it's a big enough improvement to climb the mountain of inertial standard notation has in it's favor. I'm typing this on Qwerty keyboard too, yep.