I was at an Astros - Mets game last year... it was Oswalt pitching against Mike Pelfey.
the gun at the stadium was reading that Pelfrey was throwing consistenyly about 4 mph faster than Oswalt...
But there was deninitly something 'harder' looking about Oswalt's pitches. His ball was just gunning towards the plate... whereas Pelfrey's pitches looked like they were flying in.
Pelfrey, it should be noted, is said to throw a lot of 2-seamers.