1.) "You can change from performance to quite mode..." No, you can't. SeaTools does not even offer such an option (and others explained why). I also tried obscure internal leaked Seagate tools. Nope. Can't change it.
2.) "not performing in line with it's manufacturers specifications" - In your quote it is clear that the 320GB model has 11ms t2t time, so adding the average latency of 4.16ms gives about 15.2ms, which is more or less what I measured. (16.5ms - HD Tune has probably some application, OS, driver etc overhead)
PS: Oh, now I see the thread ended in feb 2009 and not feb 2010 :-p