I'm kindof confused by this thread. I do have a ST. You can sideload any epub without DRM using the USB cable. PDF is a little more complicated. Some pdf files are just scans. You can load it, but you can't read it. Other pdfs are optically scanned - they FLOW into the program and can be read as easily as any epub. Calibre can convert some poorly flowing pdf files, but it can't fix what are essentially graphics.
I haven't had the SD card long, but it has made the side loading processes easier, especially when it comes time to remove some books.