I just got a really sweet one for my birthday, and all I have to say is Gore-Tex is GODLY. It's SO nice, light, breathable, and still good for (it claims) up to 6 hrs of constant downpour. I haven't yet tested it for 6 hours straight, but I've found that if I'm wearing it while I ride, once it stops raining, the ride dries it off again fairly quickly, so I can't see it becoming saturated...It's GREAT stuff!
I have pretty good Gore-tex gear (IXS stuff) so I don't usually need a rainsuit. I do have one though, that I keep with me if I am wearing my leathers and think t might rain. I have a Triumph Chevron suit. Really good quality, around $90.00 or so. It has an "inverted Y" front zip (unds down the center and down each leg) that is fairly quick to get into. The down side is it's fairly heavy and so it doesn't pack super-small. It does come with it's own storage bag though.
Very water-proof in driving rain on the highway & quite comfortable.
I have also heard good things about the Teknic suits, but haven't had any first hand experience.
I have my white Dainese rain suit, I've used it a couple times, but normally I get nice weather for track days. But I don't let rain ruin it, just swap on stock rims with wets on em and throw on my rain suit!