I have the Giro E2 (considered one of the top-of-the-line Giro MTB helmets) and although it's expensive, it is still cheaper than a lot of road helmets (compare to the Pneumo for instance). The venting is more than adequate at both low and high speeds and I use it for both road and MTB rides. I seem to see helmets stated as MTB helmets at much cheaper pricepoints than their road-counterparts. Whether or not you leave the visor attached when road-riding is a personal thing.