Whole Foods Market

Last week, a brand-new Whole Foods Market opened in Napa. I wasn't part of the opening day crowd - I heard traffic was so bad that people had to park several blocks away in the residential area surrounding the little shopping center and that traffic backed up into the rather busy street the center is located on.
It's a very nice store (they all are) and it's big - you can do your shopping and your walking for exercise all at the same time. There's fresh bread (really good bread), a gelato bar, (almost) fresh pizza, a wine tasting area, a salad bar, steam tables for all kinds of interesting foods (although I don't trust that it's that safe. How do I know somebody hasn't sneezed into it?) and all the usual stuff one finds there.
I wonder at the wisdom of the location, though. It's in a small shopping center (with limited parking which was a problem before this store opened) 3 doors down from a Trader Joe's. Obviously, it's nice for us consumers. We can walk from one to the other (if we've managed to find a parking space). But won't this affect sales for one or the other retailer? Are the customers who used to shop at Trader Joe's now going to shop at Whole Foods? Surely, they are not going to buy twice as much now. I'll be watching that and the big discussion about traffic and parking that's been ongoing ever since Target opened in the old Montgomery Ward store in the same center.