These are a couple of things I've been dealing with over the past few weeks that I think should be addressed.
#1) Simulator emulation for native text fields and other simple native controls like Text Box. The build process is just too excruciating to rapidly test these things. Even just a simple rectangle would be nice so we can deal with positioning.
#2) Return key manipulation for text fields. Impossible to dismiss keyboards right now or at least very very hard without return key manipulation. It's annoying enough in actual Objective-C for good keyboard behavior, via LUA I have no idea where to start and the docs don't cover it.
Overall, form support in Corona is lacking. Things like placeholders for fields in simulators and maybe a good button factory method would be hugely welcome additions.