Bought an iMac 4k (base model with 1TB HDD) last Saturday and I love the display but the 1TB HDD sucks. I thought that I could live with it but its just too slow. Yesterday, I bought an external USB3 SSD drive (on sale at Best Buy, 480GB for $159), used Super Duper to clone the drive and set the External USB as the boot drive and boom! much much better speed. I debated getting a Thunderbolt drive instead of USB3 (I still might) but for right now, the speed is good. Any drawbacks to working this way permanently? Any technical issues that I may be missing? Since I'm still a week into my return period, I could just return this iMac and preorder a 256GB SSD but the seemed like a cheaper solution. Thanks!