personaly speaking i'd do it, any time spent flying with an instructor will improve your general flying standards, and as already said, it could provide you with a "get out of jail free" card, if things start turning smelly.
i was, however alarmed at some of the posts on the last thread on i.m.c.'s regarding the benefit of flying in reduced w/x conditions.
yes i know people who do use the full privilages of the rating, their usually v. expierenced and few and far between, and yes people without said expierence also have. unfortunately some of those aren't in a position to respond. one such tradegy resulted in the c.a.a. seriously reviewing the whole concept of the i.m.c. as a valid rating.
reduced vis, getting dark, lowering cloud base etc. etc..... would you really want to hours building in those conditions?
yes a very worthwile rating, just remember
i.m.c. does not = i.r.
wannabe's do not belong in the a.a.i.b. bulletins. there's nothing worse than being "up there" wishing you "done there"!