Right off the bat, the n30's dated mechanical tracking mechanism puts it at a disadvantage. While the n30 tracks perfectly for gaming, it's just not as precise as the newest optical mice, and it also needs to be cleaned regularly. Combine that with an awkward form factor that's geared more towards precision than comfort, and the n30's few excellent features are a tough sell. Despite its perfect mouse wheel and intelligently placed third button, the n30 is hard to recommend over the current crop of optical mice.
My recommendation of the n50 Speedpad, however, is just short of glowing. The Speedpad is not only much cheaper than the n30, it's also a unique idea that's almost flawlessly executed. The layout is great; the software is excellent; and the Speedpad is comfortable, even after hours of gaming. In fact, the Speedpad is only a gel or foam pad away from perfection.
It's odd that Belkin suggests the n30 and n50 be used together, because the two devices couldn't be more different. Unfortunately, they're not really symmetrical, either; southpaws beware. For righties, Belkin scores a definite success with the n50, so long as it's paired with a better mouse.