[whpalmer4]

Unfortunately, at the moment there is not a practical way to do so from anything but OmniPlan, which runs on Mac and iPad only. On the other hand, a refurbished iPad 2 from Apple is only a few hundred bucks (and your copy of OmniPlan will run on it).

This state of affairs (not being able to edit without either Mac or iPad) isn't something I expect to change any time soon, so you shouldn't buy in thinking that you only have to hang on for a few months before they deliver the Windows version.