Inputs are an awesome addition! But it feels like they're missing 2 basic interactions that inputs have in applications and on the internet: actions when you press Enter and when you press Tab.
Enter is the more crucial of the 2. When you press enter, that's usually when you want your input to extract that string and make use of it. Currently, inputs call a function on a character per character basis, which is a good functionality to have, but not the first one that people would want from inputs.
When you create an input, there should be few new parameters: "enter_function" would trigger whenever the player presses enter. "input_function" would be renamed to something like "per_character_function" and would trigger with every character entered, like "input_function" works currently.
There would also be a new parameter called "next_input_id", which would indicate which input you'd switch to when you press Tab inside this one. Tab-switching between inputs is really useful when you have to enter lots of data in several fields, which good tools like the [URL="http://steamcommunity.com/sharedfiles/filedetails/?id=965795906"]button visualizer[/URL] do require.
With both of those in, inputs would be really powerful.