Well, NAS monitors S.MA.R.T, but its very cryptic and only "yells' if the HD does not past the test, when this happens, its mostly to late. I use on my PC
http://www.ariolic.com/activesmart/index.html, this tool has also bugs (when 1st HD does not have temp value, second HD temp alarm does also not work, also some temperaturs are offset on some HD), but its pretty good to let you know wehn parameters change and when it detects a pattern in change it will predict pretty accurate when your HD will fail. I my case on 2 HD it was very accurate in prediction when HD will fail totally, one 2 month on the other 4 month ahead before the HD was completely down. In my opinion this is a lot more help then SMART in NAS provides. So i believe, if you are spoiled with a SMART display like this then NAS light is not state of the art. Maybe a better documentation how to use the information in the SMART logs in NAS light would help, I tried to do some research, but the parameters are different on different HD and the display of the values does not help a lot. But maybe its only me that I do not have enough knowledge.