I have a Mid 2011 17" MBP with 8GB RAM and 500gb 7200rpm HD. I always have tons of safari and chrome windows open with several XCode projects, photoshop docs etc. All this leads to lag and beach-balling. Unless there are some serious coding problems causing infinite loops etc I assume this lag is down to reading from the hard drive. i.e the system is using the swap file on the hard disk. I am hoping this problem is gone on the rMBP as it uses an SSD which has over 20x the random read performance. Does anyone have any experience going from MBP to rMBP in terms of heavy multitasking and lag?