EasyBCD is just an editing tool. You don't need to remove it. In fact when you've got HnS successfully booting and hiding things for you, you'll use EasyBCD to edit the timeout to 0 in Vista's menu to remove the second (now redundant) boot menu. (Unless you have 2 Vistas, in which case the second menu will allow you to chose between them).
HnS surplants the Vista bootloader, and hands control to XP itself (after doing the hiding), so the Vista BCD no longer has to do that task - hence set its timeout to zero once you're happy that HnS is doing what you want)
Don't change or delete anything else in the BCD though. It's handy to have it all there as a fallback if Vista overwrites the bootmanager and resumes control (as it did with SP1)