My race car engine builder/mechanic friend tells me that with newer engines the machining process has improved so much that you don't have to be nearly as careful during break in as before and that even driving like a madman from day 1 probably won't do much harm (he also noted that on the race cars he just runs them for a couple minutes to warm them up and that is the extent of break-in). I guess this is evidenced by my car (1985) says 2000 miles, the next car (1994) said 1000 miles, the next (1998) said 500, and now we have 300.