if you are planning on rooting your phone then you don't need to flash it with a generic rom first, you just need the goldcard in the phone when you begin the process. the thread on modaco gives you the step by step guid, if you follow that you should be ok.
I've already flashed to generic rom to get rid of the Orange apps and demo's. Was just wondering with all this talk about it being an easier process without a gold card.. etc. Will read up on the thread, thanks.