I bought a 500 GB LaCie NAS and it has been so-so. Within the first month the hard disk within it died a noisy mechanical death. It was replaced under warranty. It is slow, not even maxing out my 100Gb/s ethernet when I'm copying files to it. It occasionally looses its mind, won't allow you to connect to it via the web based management with a browser. To shut it down you have to push and hold the power button. More than once it has been completely locked up and required a power cord pull... The final analysis: it works, but I don't think I'll get another one. I also have a 250 GB WD Passport external, USB interface drive. That is considerably faster than the NAS. (granted, USB 2.0 is what, 480 Mb/s?) The only thing the NAS has going for it is sharing files across multiple computers simultaneously.
For backup, I use a combination of bash scripts, rsync, and tar. (Linux system)