I say go with the 4.6V8. As you have seen, it is pretty awesome and all the bugs are pretty much out of it, so you won't get any surprises down the road. Later, when you can afford more, you can always add a supercharger and get the 100+ extra hp, if you want.
My past experience has been that you are best off in reliability if you wait until the 3rd year of a new production model. Defects in the first year are just being discovered while the 2nd year is in production, so they really don't get fixed until the 3rd year. It is fun to be first on the block with something new, but for reliability...wait a bit. And at the price difference...you'll love that V8 in the 2010!