Flechero - The new suit is extremely buoyant because it is made entirely of polyeurathane or however you spell it, while the top of the line Speedo is still made of a fabric. The increased buoyancy increases your speed dramatically. I don't know if the German took steroids or not, but 7.5 seconds off of your mark from the previous year has to raise an eyebrow.
Matt Fly - FINA is in the process of banning the suit, but couldn't complete the ban before the Rome races. The german racer may have "peaked" this year, but is it possible for his peak to increase his previous time by 7.5 seconds? Also, if I understand correctly, Bolt was new to the Olympics and was relatively unknown. The guy who just beat Phelps was just an average Olympic swimmer in the past, now he shatters the WR and destroys his PB from the year before.