One of the apps that I reinstalled was my EyeTV 2 software (I have the Hybrid USB model) but what I wanted to do was copy across all of the channel information and favourites to save having to re-tune everything again later.
Although I managed to find a few of the files needed, I missed some and as a result ended up doing what I wanted to avoid and re-tuning in all of the channels. This provoked me into writing to Elgato's technical support and after a couple of days they responded with the answer to my woes, so I thought I would share their response here so that those of you out there in a similar position can avoid my fate :)
The EyeTV preference files that contain all of the relevant settings are stored in the following locations and files;
In /Library/Application Support/EyeTV
Copy the whole folder
Backing up these files and copying them across to a new installation should retain your settings etc.
Hope this helps someone.