I have a mid or late 2009 Macbook that I bought February 2010. I have upgraded the Hard drive and the RAM to 6GB's. Sometimes Mavericks is sluggish (especially at boot up) but when it gets running it runs well with the additional RAM. Will Yosemite require more disk space to install and will it be more sluggish on my Mac or will it run the same? Generally Mac OS updates slow down the machine, but I am not sure if Yosemite will follow Apple's traditions.