I have submitted a folder update to Apple which should address some concerns as well as make folder more desireable to use.
First, folder now makes it obvious that it is empty. You will see a notification in the title bar as well as a blue image that tells you folder is empty.
Second, there is now an edit button in the top left corner which will turn on delete mode. There is much confusion on deleting files right now and I would like to stress again that you CAN currently delete files from folder by swiping your finger across their names to bring up a delete button.
Third, a notification should always come up for any given type of file. For some files apple will not put up a "send" dialog even when they should, so I've added an alert that notifies you that folder cannot do anything with the file. Additionally some files have the option to "Quick Look" like Mail has.
Finally, I have added a preview mode for both documents and media files. This works similarly to mail with the exception that you have to turn on "preview" mode first. For example, I was able to preview xls, rtf, pdf, doc, mp3, wav and many other files through this viewer.
I have omitted the email option for now as we have had virtually no feedback on anyone interested.
Enjoy your folder and please drop me an email or post here with any suggestions!