it is not understandable for us, that in izzy you have to learn programm a arduino bevor you can use its i/o possibilitys. and a sound soft like ableton do it in a side way, without any need to get a programmer and lose time for art of video.
Here's the simple explanation of why they have that feature and we don't (yet):
TroikaTronix has 5 full-time employees (and Mark codes the entire program himself); if we made $18,500,000/year and had around forty times as many employees as we do right now Isadora would have all sorts of neat, new features. (It's not really a fair comparison.)
The addition of a native implementation of the Firmata library for Arduino in its own actor (or user actor) is a good feature request though, thank you. We'll add it to the list.