Bladed spokes do not cause enough of an increase in surface area to cause handling problems in crosswinds. The problem is generally caused by the deep section rims used in conjunction with the spokes.

+1. Bladed spokes by themselves do not cause enough of a difference to warrant use by most recreational riders. However, in conjunction with with radial spoking, less spokes and deeper section, aerodynamic rims they are justified for competition, particularly time trials and triathlons.

Also note that here is difference between bladed and oval spokes, the latter being much more aerodynamic.

Finally, be aware of the possibility of flange failure. This was fairly frequent using bladed spokes where the holes had to be slotted. However, it can also happen with oval spokes, particular in older, less expensive hubs not intended for radial spoking patterns. In traditional spoking patterns, the angle of the spoke places more distance between the hole and edge of the flange than a radial pattern, allowing more metal to carry to load. Less spokes also involve more tension and higher stress on the flange.