Too small, but just right.
The Razer Spectre mouse performs quiet admirably, especially given how small and light-weight it is; both of these playing to its advantage rather than detracting from the whole experience.
The APM lighting system on the Spectre isn’t as obvious as that on the Marauder since the LEDs on the Spectre aren’t as apparently visible. For sure, it certainly adds to the whole APM Lighting System experience when the Spectre is paired with the Marauder keyboard. And this is one of the biggest downfalls of the Spectre, and probably the only one, in that it only makes sense to have it when it is paired with the Marauder keyboard. On its own the Spectre mouse looks a little out of place, you would do better with any of Razer’s other offerings, such as the Imperator.
Ironically the Spectre mouse is a more all-round experience for regular use, outside of StarCraft II, compared to the Marauder keyboard which seems specifically designed for StarCraft II. I would be hard pressed to recommend one over the other; if you’re going for the Marauder, then you should definitely get the Spectre (and vice versa, of course).