No problems. Actually if you get the chance, look at the construction kits released for PC version of Oblivion. It's incredible how quickly and easily it is to throw texture layers on that platform.
Most likely, they put the majority of layering work into new textures, and updating older ones. But recycled textures can probably be tossed on in less than a week, and really bring the game up to shine. Most games usually have about a 90-60 day period before it goes gold to debug, and perfect everything. A lot of work happens in that time, and once it goes gold is when we'll see just how good it is. Glad to help : )