My MacBook is almost three years old and is getting very sluggish. I will be upgrading to a MacBook Pro next year but in the meantime, would a clean install improve the speed? I have all my files backed up on an external hard drive. I'm not necessarily looking at restoring from backup, as I think it would be nice starting out "new" and only copying over things I need need from my external. What do you think? What are the pros and cons of a clean install? Thanks.