We used a sim a hell of a lot during my IR course to get the cockpit procedures sh1t hot and fly approach after approach so when it comes to the real thing you have everything clear in your mind and know what you are going to do. Its a case of £35/Hr Vs £120/Hr in the air!!
Do it, I spent a whole day on it once getting really beasted by my inctsructor and was absolutely knackered at the end of it, but the difference was incredible.