Primarily, it's intended as a direct replacement for traditional "candle" style incandescents, providing low level atmospheric lighting.  The diminutive size, low colour temperature and E14 cap make it an ideal candidate for this use.  The fact that it produces a (relatively) insignificant amount of heat and has a rated lifetime of 10K hours also help there.

The other application is in security/emergency lighting.  The low power consumption of this lamp and long lifetime mean that it is an ideal candidate for low level round the clock illumination and for emergency lighting.  According to the information in Osram's Dulux Lamp Catalog, the current version of this lamp (and it's 7W version as well) are capable also of running on a DC power supply - a real bonus for backup purposes.

As somewhat of a sidenote, the tube used in this lamp is also seen in the Osram Dulux Mini - a small battery powered lantern, which can be found on my Flashlight Reviews Page.