The Progress API/COM syntax are a more unwieldy version of VB syntax for accessing components and libraries, as it is an interface to the same. Your antipathy to MS seems rather odd given that it's front end development tools are in a different league to Progress, and you are interested in the normal ADE.
You should be ok for a while continuing to develop in the standard AppBuilder, but you will be hobbling yourself if you make no attempt to move with the times. As far as Front end development in Progress goes, this means either looking at .Net, or some other front-end environment, eg. Eclipse (which Progress is tying itself in with). Both frameworks should allow you to develop (in theory) more advanced, better-looking interfaces than Progress Appbuilder alone.
As has been stated before, Progress seems to be positioning itself as a business/data service provider with easy integration with Front End frameworks it can not compete with.
You would do well to concentrate on developing your general skills in Progress (particularly at the Business/Integration end), and complementing them with other development technologies, particularly on the Presentation side.
That's what I intend doing, anyway.