Although some information on this page is relevant, it is outdated by a few months. A new version of Manjaro is out and there is a separate review for it: http://profectium.blogspot.com/2012/11/manjaro-linux-82-review.html
Manjaro Linux is a Linux distribution based on Arch Linux. Arch, for those that do not know, is a distribution designed to be completely minimal; this allows the user to build their system from the ground up. Manarjo is Arch Linux for people that want a functioning system out of the box. Using Manjaro still awards the user with the features of Arch Linux while being wrapped in a user friendly package.
Manjaro Linux is very easy to install. It uses X by default but still uses an ncurses user interface that opens in a terminal to install. The installation takes considerably longer than any other Linux distribution I have ever seen before, mainly on the formatting part. The partition editor did not recognize my other partitions either, so I had to use the entire disk. The problems with the installer will be fixed some time this fall when the Manjaro Linux team finishes their graphical installer. If you have ever installed Archbang, it's basically the exact same experience.
Manjaro uses the lightdm display manager just like Ubuntu does. There is a sacrifice between memory usage and aesthetics here, however. Lightdm uses about 50 MiB more RAM than gdm does, and /etc/inittab is nowhere to be found. For those that do not want to kill lightdm and start X manually on every boot this could be a dealbreaker. I was not happy with this.
When choosing which CD .iso to install I chose XFCE. To my surprise it was heavily patched for Manjaro Linux. The entire XFCE experience was wonderful in terms of additions that the Manjaro Linux team made. I presume that the other desktop environment options are just as friendly if not moreso than the XFCE version of the distribution.
Prolonged use impressions *new*
I have recently discovered a very troubling bit on information about Manjaro. If you notice in the screenshot, 585 MiB of RAM was in use. This is a nominal sum in today's age, where having 8+ GiB of RAM is commonplace, but what is using all of that memory? It turns out that a kernel module named nvidia was installed during the Manjaro installation.
It dawned on me that Manjaro DID provide a boot option to not install video card graphics drivers, but I instead installed the drivers. Following this guide I blacklisted the nvidia kernel driver and restarted the kernel. Upon doing this X was completely brought to its knees by the absence of the Nvidia driver. X DEPENDS on the Nvidia driver as it is used in Manjaro Linux.
Manjaro Linux does not provide a flexible graphical system to meet the needs of a graphics-intensive user as well as one who does not use graphics. Rather, they polarized their distribution with two extremes that conflict with one another.
Unlike Archbang the pacman (package manager) mirrorlist is functional right out of the box and does not need any updating. Pacman even comes with a graphical frontend, making installing software possible for beginners.
The autoconf tools suite was not there by default, however. This made installing packages from the Arch User Repository (AUR) difficult. Any user wishing to compile their own software will also have to take the detour of manually installing the three packages that make up autotools.
Non-manjaro specific Arch Linux evaluation
Arch Linux, the system that Manjaro is based on, has quite a bit going for it. It is arguably the best documented distribution around with its wiki and forum. The AUR and official repositories are as up-to-date as portage, which until now has been the best repository tree I have ever used. Pacman is a bit cumbersome to use from the command line (pacman -Syu to update does not make immediate sense), but it is one of the selling points of Arch Linux.
If you are a user interested in Manjaro Linux it is completely usable as-is. For a user with a bit less experience with Arch Linux it would probably be wise to wait until the graphical installer is released to avoid the partitioning confusion that all users of Manjaro have run into so far.
After discovered the issue with X recently I have decided to jump ship to Fedora Linux. However, it is a very minor issue since the nvidia module only takes up about 111 MiB of RAM. The scary part about the issue is that other shortcuts like the X-dependency or lightdm could be lurking in the background of Manjaro Linux, making it an unreliable computing platform.