We use RTF format to generate documents in our products as it is widely supported by software vendors. The bad thing about RTF files is a file size, which drastically increases when document contains images (compared to the same document saved in "doc" format). This becomes a big issue when you have hundreds of thousands documents stored in a databases, and send them to other parties.
As it turned out, the file size issue is not caused by RTF format itself, but by the way MS Word saves RTF files with images. When MS Word saves document in RTF format, it saves two copies of each image - original one and also a copy converted to WMF format. Fortunately, there is way to disable such a strange behavior. You can read how at Microsoft knowledge base article Document file size increases with EMF, PNG, GIF, or JPEG graphics in Word.
As it turned out, the file size issue is not caused by RTF format itself, but by the way MS Word saves RTF files with images. When MS Word saves document in RTF format, it saves two copies of each image - original one and also a copy converted to WMF format. Fortunately, there is way to disable such a strange behavior. You can read how at Microsoft knowledge base article Document file size increases with EMF, PNG, GIF, or JPEG graphics in Word.