The hours arent loggable, you know that already. Should you mention it in a CV? Personally, probably not as it makes no difference to the actual total time. I would however mention in a couple of lines in a covering letter that I had gained some experience in a covering/assisting/safety(call it what you think appropriate) type role, assuming of course its a reasonable amount of exposure to the role and not just a couple of right seat jolly's. It shows commitment and enthusiasm. In years gone by some smaller operators employed right seat pilot 'Assistants', not sure if that sort of thing still go's on. As others have mentioned though, its good experience and assuming its in something with reasonable performance like a King Air then it puts you in the real world IFR environment which is good exposure. The MEIR teaches nothing other than procedures, it doesnt teach real world flying. I fly with new FO's regularly, most of whom are typical low houred frozen ATPL's. As well as getting to grips with the aircraft and the procedures, theyre also trying to get to grips with the radio and the environment, and in particular the pace of that environment. Most have come from a GA/instructing background so any previous IFR time in a TP is good exposure, whether loggable or not.