They all use complicated methods even if sometimes scripts or graphical interface are provided to hide.
There is however a very fast and simple way to make a .iso bootable on USB, isohybrid script provided in recent syslinux. It works quite fine except that some BIOS and some partitioning tools don't like that the first partition says it starts at 0. We have a very simple patch on Mandriva to make it work on such machines. We used it on Mandriva 2009 Spring RC1 GNOME Live iso and got no negative report, so it is now used on all Live CD since RC2.
Actually we got several negative reports, but it was always because people copied the iso into the first partition and not at the beginning of the key (i.e. onto /dev/sdb1 instead of /dev/sdb) despite it was stated quite clearly on the wiki: where /dev/sdX is the path for the device of your USB stick and X is a only one letter (not one letter and one number). For instance /dev/sdc or /dev/sdd are correct, /dev/sdc1 or /dev/sdd2 are not correct and won't work..
Because of that, we now have a graphical interface (based on Fedora LiveUSBCreator for the UI) which allows you to select the iso image, the usb device and perform the copy. Windows version will arrive soon.