Curved tubes can be aesthetically pleasing and are sometime functional (chainstays/seatstays for tire clearance, seat tube for short wheelbase, fork blades for some level of suspension or for unicrown designs). But it is true that they are slightly weaker and heavier (longer, and thicker-walled if mandrel-bent) than their straight counterpart. If they are properly designed the resulting bike should be perfectly reliable, and I'm sure the Wilier is.