Hi guys, I ordered the 2012 iMac, after some seriously consideration, I've decided to go for external SSD instead of Fusion Drive or self-installed blade SSD. As I posted in another thread, I thought the Thunderbolt interface will throttle the overall performance of the SSD. Now my expectation is confirmed. I purchased a LaCie Rugged USB 3.0 Thunderbolt™ Series for ~$230, which is a 1TB external HDD with a Thunderbolt port and a USB 3 port. Then I ripped it open and swap the 1TB HDD inside for a Samsung SSD 840 Pro 256GB. 840 Pro is the fastest consumer SSD available in the market, so the real capability of the enclosure can be seen. Then I plugged it to a 2012 Mac mini with 2.3 quad-core i7 running Windows 7 (BootCamp). Fig. 1 is the AS SSD Benchmark result. Out of curiosity, I also test it through its USB 3 port, result is shown as Fig. 2. As you see, the Thunderbolt enclosure can only unleash ~1/3 of the 840 Pro. 840 Pro can easily score more than 1000 in AS SSD when directly connected to SATA 3. It even cannot beat USB 3 in terms of random r/w (4K 64-Thread is not important for home usage). So, if you want to put your SSD outside to boost your new iMac, a cheap USB 3 case can handle this task. And if you want to stick with Thunderbolt for some reasons (daisy-chain, old Macs without USB 3, etc.), a entry-level SSD is more than enough, since the limit is the Thunderbolt interface (I am talking about single-drive enclosures only). Oh, if performance really matters to you, you'd probably better to open your iMac up or simply order 768GB SSD... Good thing about TB For OS X only user, the performance margin TB brings doesn't worth the premium. BUT, if you run Windows on your 2012 iMac and you what to enjoy SSD speed, TB enclosure is your only choice other than hefty 768GB SSD option. Fusion doesn't work for Windows (BootCamp) partition. You can firstly install Windows into your internal HDD then copy your Windows partition to your external Thunderbolt SSD (using Winclone). Then you are set. Yes, that simple! You cannot do the same thing with USB or FireWire enclosures. Windows can only be booted from a internal disk, but TB disks are treated as internal SATA disks. I've successfully done that with my 2011 MBP and my 2012 Mac mini. Hope that will help.