The idea of sharing ones room with an exact duplicate of themselves is truly a unique and interesting one, especially if the person who does it is Arnold J. Rimmer.
The concept is great, but I think it was it's execution that didn't work for me. I suppose after reading the book, and seeing how much further they took the concept there, this episode doesn't look as good. Also, 2 Rimmers can be quite annoying, especially when they yell, which is quite often in this episode.
Still, there are some great moments. The final scene with Rimmer satisfying Lister's curiosity is well written and acted, and allows for some last-minute characterisation of Rimmer. The Cat's reaction to Rimmer's tragedy is priceless.
Despite some great moments and concepts, this episode isn't really one that I like to watch again.