We were there from the 8th-12th Sept last year, the week started off very quietly, no lines, I think we waited about 10 minutes to get on Nemo & only 5 minutes to ride Soarin' & Grizzly River
It got a little busier on the Thursday & the Friday was a lot busier, but we never needed to use Fast Pass & really only had to wait for Toy Story.
We were there from the 8th-12th Sept last year, the week started off very quietly, no lines, I think we waited about 10 minutes to get on Nemo & only 5 minutes to ride Soarin' & Grizzly River
It got a little busier on the Thursday & the Friday was a lot busier, but we never needed to use Fast Pass & really only had to wait for Toy Story.
We were there last year the 13th-20th. It was really slow with almost no waits except with TSMM and Nemo and those were 45 min. We are going again this year the 20-25th but I am thinking the crowds might be a little worse this year. Look at the closures during your trip so you won't be disappointed...
We went in Sept. 2007, and it was quiet. I would not expect that this year though. This year, you have the 5 for 3 going through the end of Sept. You also have some big conventions. We are there Sept. 12-20 this year. Sept. 10-13 is the D23 Expo with big crowds expected. During the week is a convention at the DLH and a homeschool convention at the GCH. The next week is a huge convention that apparently has booked the entire convention center. I don't think that it will be near as quiet as a couple years ago.
ETA: I think I read somewhere that Space Mtn. will be closed for the same dates as HM to add a Halloween overlay.