Have no default output selected. Require a choice the first time it is used.

The idea of "Start conversion immediately" is great, bu there are three problems:
1.) It doesn't actually start immediately. I still had to select "Start". I should be able to just drag and drop files and have it go. I saw no difference with it on or off.
2.) It isn't large enough. It is easily overlooked.
3.) Selecting the output is also by default, so you can accidentally convert to the wrong format. Please consider putting the "Start Conversion Immediately" check box up next to the output format selection. Also, consider putting the output format selection at the bottom. It seems more user friendly to select your input, then your output, rather than selecting your output, then your input.