Is Manjaro just an easy-to-install version of Arch?

No. Manjaro is unlike other Arch-based distributions such as Archbang or Bridge Linux. While there are numerous subtle differences between Manjaro and Arch, the most obvious examples --including the use of our own dedicated software repositories-- are covered in the About Manjaro page.

De:
http://wiki.manjaro.org/index.php/Manjaro_FAQ