I've messed with operating systems on other devices like MP3 players and installing linux and such on them, but the problem with many devices is that you have a chance of bricking the device to the point where it can't be recovered.
These TomTom's are almost impossible to brick. By deleting the software alone you cannot brick the device. I have actually formatted both the SD card and Internal memory at the same time just to see if the Home software can recover the device from scratch, and it sure can. It will reinstall the map and OS fresh. The trick is deciding what to install where. I have a 4GB SDHC card, so what I did is just installed EVERYTHING onto the SD card (os+map+everything) so it makes life easier for me for when I have to "select device"
The beauty of GO models is that you can mix and match files between SD and internal memory, and the device will read from both at the same time.
Always make sure to make backups as well just in case.