there's no such thing as 'breaking in' a new machine as far as hardware is speaking.
If you copy of OSX was installed years ago, or has been upgraded (or upgraded more than once!), you need a clean install of OSX to get your full performance. Everybody trashes M$ windows because it gets slow and bloated with use. nobody realizes that as great as OSX is, its still an OS, and still gets 'dirty'.
You can also look at how many unnecessary processes your machine is running at startup