I got a MacBook Pro 2.9 GHz, 8Gb memory in July. I have updated the operating system to Mountain Lion. It had a few problems very early on – the battery failed, was replaced, failed again, then another component was replaced, which seemed to solve the problem. Since the last repair it started up a bit slowly and this seems to be getting worse. At present it takes 1min10secs to get to the login screen then another 1min 20secs from there to open up a web browser, which is frequently unresponsive for a bit longer while the computer gets ‘settled’. Once everything is up and running, the computer is reasonably quick and responsive.
I think I have checked most of the obvious things. I have removed all login items, there is 500Gb free on the hard drive, I have verified the disk and disk permissions, and I have checked Activity Monitor – at most 10% of CPU is being used while the computer is still slow and unresponsive and there is always 4Gb of memory free.
The standard hard drives that comes with Macbook Pros are not that fast (only 5400 RPM) so you won't be expecting a blistering fast Macbook. Since you already ran the disk utility try reseting the SMC http://support.apple.com/kb/HT3964.