HD Native with iMac and Akitio Thunderbolt box

I made a switch from 2010 Mac Pro 6*3.33 to 2013 iMac 21.5" i7 3.1GHz. I moved my HD Native PCIe card to Akitio Thunderbolt enclosure. What's important, my iMac has 1TB Fusion drive which initially people reported as problematic. At this moment I run it on OSX 10.9.4 with Pro Tools HD 10.3.9 software and I experience no problems. The system is actually better and more stable than the previous one. No errors, plenty of processing power. I split my drive to two partitions: 120GB for system and 1TB for the rest. I actually run sessions from it with absolutely no problems. I tested several USB 3.0 drives and the perform awesome too. iMac is dead quiet even under heavier load. Much quieter than Mac Pro 5,1.