It's noticeable. I thought he actually improved in the second half. First half, his passes seemed to hang and were wobbly.
Ultimately, he still is among the best. It does make it a tad easier to defend him though.
Peyton Manning was like this before he really fell off. That one year in Denver when he threw like 50 TDs, he basically looked like Drew. That's the only thing that scares me is that Brees could fall off a cliff like Manning. But then again, Manning had the neck problems so hopefully that's why he declined so rapidly.