Once the dream of a living neural network is achieved, the possibilities are staggering. Evolution has shaped the mind of each species in unique ways, providing a "baseline programming" that artificial intelligence from the ground up could never hope to match.
For example: krogan mental abilities are evolved toward war and conquest. Or salarians are adapted to complex scientific considerations. The possibilities are limited only by the species we find.
Further, by wielding control over multiple subjects in parallel, we can unleash awesome computing potential unrivaled in the history of technology. Imagine what linking a million asari minds together could accomplish?