15" 2011 MBP, Logic board replaced, now my comp is slow

I've posted previously about how my logic board failed weeks after my warranty expired and everyone told me that paying for it wasn't a big deal. I disagreed and continued to call and chat with apple and eventually they agreed to replace the logic board and anything else that may be wrong.

I got my 2011 15" MacBook Pro back from the apple depot about 2 weeks ago and it hasn't been the same. Initially I thought I was crazy but its getting progressively slower as the days go on. It's taking 10-15 to reboot and opening iTunes makes everything freeze. Using a photoshop or making music isn't even an option. My computer before was super fast and could run 10s of CPU intensive apps with ease. Now I can't even play music.

Any idea what this could be? I have an apple appointment but I want to hear what others think before I go to the Apple store. This computer hasn't worked properly for more than 2 weeks at a time since I got it and at this point it's become more trouble than its worth.

Have you checked that the firmware is up-to-date?
Is it a 'clean' install of OSX?

SM

clone/back up your internal hard drive, do a clean install of OSX, complete all the Apple updates and migrate from your clone/backup to the new internal HD.
Then see what happens.

I'm trying to back it up. I'm not sure what a reinstallation would do but I guess I'll try it. They said my HDD was formatted at the depot an they backed up my HD and put everything back on afterwords so I don't know if that might have something to do with it?