Originally, I was going to get the $1499 rMBP13 2.4Ghz/8GB/256GB, and also get a 1TB USB3 external hard-drive. I'm planning on keeping the rMBP for at least 4~5 years. I'll only take the rMBP out of home maybe 1~2 times a week. But I've been thinking if it would be worth it to pay $300 extra for the 512GB model, which would also include the 2.6Ghz processor (which I don't really need). The benefits are of course the extremely fast ePCI read/write speeds, and that I could potentially not have to carry an external hd all the time. Downside is, well, $300 (minus the cost of the 1TB USB3 drive which is more or less around $100). The external hd would of course not be SSD, and would have much slower read/write speeds. Has anyone lived with always carrying an external USB drive for a few years? How fast are the external hd's these days? I'd appreciate your comments. Thanks!