http://www.topolinotech.com/technology/spokes.php as of 2007/11/04 says Topolino spokes are made of both carbon and kevlar fibers in thermoplastic resin, with carbon fiber for strength and stiffness, kevlar for strength and toughness. It also states spokes are 40% the weight of a 15g (1.8mm) spoke, with "more than three times the tensile strength". It does not discuss stiffness, whether increased strength is advantageous, durability, or aerodynamics.
Conventional tension-spoked wheels have spoke diameters ranging from 1.5mm to 2.3mm. Even the slimmest spokes (1.5mm) fail from fatigue, not from low strength. Indeed, a 1.5mm spoke is strong enough to pull out many hub flanges and rim spoke beds if sufficient tension is applied. Strength is not typically an issue for spokes. Typical lower limits on spoke diameter are (a) details of elbow manufacturing that accellerate fatigue failure; (b) torsional windup during wheel assembly, which complicates wheel assembly and field service; and (c) spoke stiffness, which affects wheel load-carrying capacity and feel.
Without knowing the stiffness of the Topolino spokes, a fairer weight comparison is against a 1.5mm spoke, the thinnest commercially available (e.g., Sapim Laser). Although the spoke is thicker at the ends, the thick section is short and the weight compared to a 1.8mm straight-gague spoke is roughly 1.52/1.82 or about 70% of that of a 1.8mm spoke. The Topolino spoke is then about 0.40/0.70 or about 60% the weight of a 1.5mm spoke. According to Damon Rinard's list of component weights (http://www.damonrinard.com/weights.htm#spokes as of 2007/11), a 291mm DT 1.8mm spoke is 6.06g whereas a 293mm DT Revolution (2.0/1.5/2.0) 293mm spoke is 4.71g. A Topolino spoke of the same length would be about 2.5g. Thus, for a 24-spoke wheel (a standard Topolino configuration) the Topolino represents about a 50g savings over 1.5mm spokes rather than about 80g savings suggested for 1.8mm spokes.
Spoke stiffness affects wheel load-carrying capacity. Suppose a wheel with a rim that is siffer and stronger radially than laterally, and with the wheel oriented so one spoke is pointed at the ground. The wheel is near collapse when the spoke loses tension and stops providing lateral support to resist further loads. If spokes are stiff relative to the rim and spoke-to-spoke spacing, a radial wheel load will detension one spoke without signficantly dentensioning nearby spokes. Because the rim is laterally flexible and weak, a lateral load will also not be supported by adjacent spokes, so a lateral load can collapse the wheel. With a more flexible spoke, a given load bends the rim farther radially, thus transferring more load to adjacent spokes before fully detensioning the spoke pointed at the ground. Thus, it requires a larger radial load before the rim becomes unsupported laterally. With other rims, a more flexible spoke may be of no advantage, but also may be of no disadvantage.
Thus, if the Topoloino spoke is too stiff, some wheels built around it will be weaker than counterparts built with light steel spokes. Wheel strength can be recovered by using a stiffer/stronger rim, but at increased weight, making the savings smaller. There is no indication of spoke stiffness or acceptable load limit for the wheels, so it is not possible to determine whether the indicated weight savings of the Topolino wheel are achieved at a corresponding reduction in wheel strength. Spoke stiffness is not indicated, or is wheel load limit, so no exact conclusion is possible. However, prudence suggests noting Topolino spokes may build a weaker wheel.
The Topolino web page does not indicate spoke durability. Field evidence indicates rapid spoke deterioration. Most spokes show modest fraying and some have dramatic fraying. The usage history of these spokes is unknown; the owner estimated two years service and unknown distance traveled (as these were one of several sets of wheels used in that time):
Frayed spokes are weaker, but how much is unknown — these wheels have not yet failed, but also clearly have a limited service life. It is not obvious how to determine if this amount of fraying makes them unsafe, prudence suggests replacement. For cost-is-no-object racing, significant spending on wheels is acceptable. For more typical cycling, cost is an important issue: expensive wheels with durability similar to that of tires and tubes is unacceptable, given that typical steel-spoked wheels can be built with similar weight, lower first cost, known strength, and durability of multiple tens of years and hundreds of thousands of kilometres.
Finally, Topoloino spokes are much larger than steel spokes, and have a yet-larger bulge at the rim end, which is the fastest-moving and thus most aerodynamically important part of the spoke. The result is higher skin drag than still spokes in all situations and likely increased aerodynamic drag in most or all situations. Thus, Toploino spokes may be a disadvantage in typical road cycling, where aerodynamics is typically considered more important than weight.