No doubt this is worth getting, it fits perfectly around the unit, and as stated in the above comment, it gives the unit that added line of defence in case of a fall. I also agree with other comments that the clip and the extra D ring on the back are a little redundant, with the lanyard fitted and threaded through its all you need and would make the whole thing look less bulky.
My word of warning... I bought mine from 'photoland_uk' and it is clearly NOT authentic. The 'Garmin' is written in completely the wrong typeface and the embossed globe logo is missing altogether. I'm not saying its of inferior quality... its just not the genuine article.