Ask Michael Rasmussen - he'd probably agree. But seriously, I don't understand why a salesperson would tell you that. Like Chris said, it's a broad generalization that may or may not apply to a particular rider. If a tri-bike were being purchased for a novice rider to be used on a highly technical course, then perhaps it's not the best bike choice. But my tri-bike (as well as several that I've owned or used extensively) can handle curves and downhills just fine.