I have a Qnap-269 (dual WD Red 2TB drives in a RAID 1), I had a Qnap-259 before my Qnap-269. The Qnap software is quite mature and robust, plus the performance of the Qnap-269 is certainly better than the EX2 (obviously … it has a faster CPU and more RAM). HOWEVER, I also have an EX2 (dual WD Red 2TB drives in a RAID 1) so I am in a good position to compare and contrast. So far I am satisfied with my EX2 because of its fantastic value. My EX2-2TB cost about $350 on Amazon, my Qnap-269-2TB cost about $575.
I love WD’s UI for the EX2 but I acknowledge WD has more work to improve overall performance (e.g., improved software efficiencies), they still have to improve their feature set (e.g., improvements to things like their USB backup and other suggestions that have been made), and they need to resolve more core level bugs (e.g., their Amazon S3 implementation is still buggy).
In summary, as a basic NAS, I think the EX2 is an excellent value.
Edit: Sorry I meant to type Raid 1, not Raid 0 … so I just edited my post.