I've found that Swype is a notable exception to the original article's statement that mobile is better for lefties. What makes Qwerty so good for lefties on a keyboard is what makes it so terrible for Swype.
First, the most common keys in Qwerty are on the left, which benefits from the angle at which a right-handed swype-motion attacks. Secondly, when using the right-hand, the keyboard is not as frequently obscured. The thumb always covers the least-used keys, exposing the more frequently used keys (those on the left) for navigation and selection. Still, with Swype, the right-thumb will eventually obscure keys for the right-handed user, but it is never as bad as it is for the lefty.
Lefties using Swype will most frequently cover the most frequently used keys, leaving the right-hand-side of the keyboard exposed, where the least-frequently-used keys reside. Also, the attack angle of the left-thumb is more likely to trigger false selections, both because of the nature of the angle itself, and (I presume) a bias in the software toward a right-thumbed attack angle.
These problems aren't so bad with two-thumb qwerty software keyboards, since they're intended to be used with both hands. In that case, it really don't matter, no more than with a standard keyboard. In fact, like with standard qwerty, the lefty might be at an advantage. Still, as a lefty, I haven't had much success with on-screen keyboards, so I do wonder if all those righties that have no problem have some hidden advantage that I haven't quite figured out yet.