Like Newspaperguy, I live in a fairly wet, cool climate, so it makes sense to use fenders, rain pants and a rain coat. I tried a poncho, and I found it to be extremely impractical on a bike. Goretex fabrics are expensive, but they breathe, and are well worth the extra money if you get rained on a lot. In very warm weather, any kind of rain gear is probably not a good idea; in temps above 65 F, getting soaking wet without rain gear is still way more comfortable than getting overheated in a rain suit and getting soaking wet from sweat anyway.
If this sounds a lot less comfortable than a car, it is. But it's a lot more fun, and over distances of 5 miles or less, probably faster.