Scrubs Season 5 and 6 definitely get goofier, but there are still some fantastic episodes. Season 7 was the writers strike season, I believe, and it shows.
After Season 7, NBC stopped airing it, and it moved over to ABC. ABC actually owned the show the entire time, though it was on NBC (I am oversimplifying this because it gets into network politics that I don't understand).
Season 8 of Scrubs gets back to the greatness of Season 1. Season 8 has some of my favorite episodes of all time. The steak night episode is a top 5 episode in the series. That ending with "I Will Follow You Into the Dark" is just classic Scrubs.
Season 9 does not exist, it never has existed, and never will exist in my reality.
I also agree with everyone above, go invest in the DVD's from Half Priced Books or something. I could not imagine watching this show without the correct music. They did soundtracking better than any show I have ever seen.