Currently it costs $300 to upgrade from a Core i5 to a Core i7 on the 13" MBP. With the new Ivy Bridge chips, what kind of performance benefits will there be between i5 and i7? I can't find any explanations or benchmarks online, all I've found is that in Sandy Bridge, Hyper-Threading was disabled in i5. Any thoughts? What's the performance benefit of spending an extra $300 (or however much it turns out to be after a refresh) for an i7?