It's not perfect, but it works 99% of the time (at least for me).
I've got about 100k on my suit, and the only times I get wet is when the rain comes from the side or I slow down or stop. For anything except a frog strangler, the RC keeps me dry. If it's bad enough to get inside the RC, anything else 'breathable and waterproof' I have is soaked too (gloves, boots, helmet, etc).
I guess the way I see it is that waterproofing is just one aspect of the function of riding. There's also protection, convenience, visibility, etc and for this, the RC is the best I've found (because I would rather keep riding instead of debating whether to stop and put in a liner under a bridge).