Max capacity
Given I bought the 5TB version of this box off the shelf (2 x 1TB + 2 x 1.5TB), I would say that the 4TB limit isn't what some people think it is; as I understand it that's the compatibility limit for individual disks which isn't exactly a unique problem.
I can live without RAID capability, it was never part of WHS and in any case the way the data duplication is implemented is robust enough and also has the advantage that you can select what should or should not be covered, rather than securing the entire volume.
The hardware isn't bad but needed a modification to the cooling - originally the disks ran too hot, now the fan is reversed and the speed control is disabled they run at a much better temperature though at the cost of a lot more noise.