QNAP made a very wise choice when they decided to build a new series based on the hardware of their Pro units with some changes that made a significant price cut possible. At the time of the review, the TS-869L was 174 bucks cheaper than the TS-869 Pro while offering most of the features of the latter. You can, if you don't care about the LCD display, the lockable HDD trays, and a minor performance drop, save some money (and spend them on HDDs) with a TS-x69L model.
The TS-869L is a high-end NAS for, mostly, high-enthusiast users or business environments. It is backed up by QNAP's excellent support and utilizes an excellent custom-tailored operating system that offers a ton of features covering everything a user or a pro may need. The TS-869L was rock stable the entire time I played with it, and it never crashed or stalled during the tests I conducted, and I had it running 24/7 for some weeks in order to complete all of the tests.

There is no doubt that QNAP has, once more, done an excellent job, and I can assure you that this NAS is worth every cent of its high price. I can't think of a reason not to recommend it if you need the storage space, especially considering that the price of HDDs has finally started to drop. I would only like to see its long boot and shut-down times fixed with a firmware update. It would also be convenient to have the option to bypass disk checking during RAID initialization in order to save some time. Finally, a longer warranty period would be great!