SmallNetBuilder

First @OSS and all those, not understanding the definition of "backup":
A backup means, that you have the original data on your main drive, and a identical copy of them on one (or n) different drive(s), so that you never loose data as long as only one ( or n-1) dataset(s) is lost. To be safe in that point, you need to have at least three copies, also should not have the online at the same time except the moment of synchronisation and store them in different locations, e.g. at your aunt's house 20 miles away to prevent distruction by local hazards (fire, water-flood, hurricane, etc.).
IF YOU ONLY HAVE ONE set of your data, no matter if its on you lokal drive or on the NAS,
YOU DO HAVE NO BACKUP!

I own(ed) 6 of those drives and four of my friends, my dad and my aunt do also own some. They are pretty fast, especially for that price. Whne you can live with the reduced feature set, it's pretty easy to handle. If you need more, you just go to your http://mybooklive.local/UI/login
Log in,
http://mybooklive.local/UI/ssh
enable ssh access here,
start your putty and log in as root, pw welc0me (Zero!)
and you have a full blown debian Lenny root shell to play around. It's not as comfortable as a gui, but you can do almost everything.

According to the point reliability:
Two MyBookLives died.
One, because my brother unplugged the power cord several times, because he was disturbed by the hdd-hummm, until the hdd's heads crashed. The drive and its data were irrecoverably lost.
The second one because our telco's outdoor-DSLAM was hit by lightning, which, in consequence, killed my modem (and those of about 120 neighbors), router, GB-switch and the network interfaces of my printer and my MyBookLive. The mybook system itself and its HDD were still ok and bootet as normal, but when it tried to take the network interface up, nothing happened. I had to disassemble the mybook and connect the HDD to my computer to recover the data. The other two MyBooks also running at that time in the network, took no harm (except for one, using its LED indicator for activity and standby). The oldest two MyBooks are just over 30 months old and still running flawlessly.
So, they are pretty tough boxes if you keep in mind, that you should shut them down before unplugging the power cord.
A very interesting and important poit is, that they are pretty quiet. They have no screaming mini-fans, they are passively cooled and nevertheless pretty cool. The only sound they produce is the humming of the HDD itself which vould be conducted to your desk even they have rubber feet. To reduce this, take a thin soft rubber pad (anti-slip or something similar) and place it between your desk and the MyBookLive. The result ist, that you have to look at the status LED to see, if the drive is running, because you almost can't hear it, even in a veeery quiet environment.

So, to tell a long story short:
A pretty good deal regarding speed, storage, energy consumption and quietness. Easy to use if you can live with the shortages or flexible, if you are able to hack on a linux console.

pros:
- it's so fast that it knocks out every competitor unless they have a atom processor an cost three times as much as the MyBook without having HDDs installed
- it's really quiet. Same-Spped-Competitors have fans
- it's almost as cheap as a usb drive (15 €/20 $ difference) but accessible via net/wifi
- pretty reliable, if you don't mistreat it
- easy to use OR very flexible and extensible
- MyBookLive to MyBookLive Backup implemented
- its really energy-saving compared to competitors

cons:
- you cannot exchange the HDD (without loosing warranty) or install a second one
- no usb extension port for printers or 2nd HDD
- no usb port to connect it directly to your computer
- GB Ethernet connector only
- limited features in gui, uncomfortable in console mode, but very flexible then
- does sometimes not survive lightning stroke or little bro's attacks :-D

Sorry for my "extendable" english, I know that it should be better.

I already own a few Western Digital drives and I find them reliable as long as they rely on USB or FireWire. Sadly, the server edition (Live) is far from being as reliable. An employee from a computer store I regularly go to told me he had many returns as well. I would not recommend this drive although it has quite a few interesting features to offer. I won't review them here since the drive tends to fail too often and reliability being the number one feature one seeks into this type of device, all's said.

I bought this 2 months ago, Due to power outage the Hard disk stopped working, It contained all my important data, I took out the drive just to find out that its damaged internally.

For me it was waste of money,time and resources. I will never recommended to use this as your primary backup

Got the first unit in May 2011. It dies in June. In-store replacement. It died again at end of September. I will not seek to replace it this time. The end.

Newest firmware adds NAS backup and the WD 2 GO replaces mionet so you can access these drives from anywhere through an easy web interface. Android and iOS apps as well.