The mobile Maxwell die
The Maxwell GPU's superior efficiency means that it should offer a significant performance improvement over Kepler, even with the same number of cores. Clock speeds are also up sharply from the previous generation -- the older GeForce GTX 680M and GTX 780M were clocked at 720MHz and 823MHz respectively, while the 980M is running 26% faster.
All of these improvements are aimed at closing the gap between mobile and desktop GPU performance, and pushing above the 1080p mark. We'd advise against reading the graph above too optimistically -- the advantage of using fat computer icons to represent data points is that it makes the gap look smaller than it is. NVIDIA's FAQ states that the GTX 980M should perform at roughly 75% the performance of the GTX 980. Even that seems low, given that the GTX 980 desktop packs 33% more cores as well as higher clock speeds, but it doesn't change the fact that the gap between the two platforms is shrinking over time.
All of the GTX 980 features that we discussed in our initial review are present in the new cards as well. Dynamic Super Resolution will be added in a future update, as will support for the new MFAA antialiasing standard. Other capabilities, like the VXGI voxel acceleration engine that NVIDIA is pushing hard as a major feature of the Maxwell family are also supported, though no games that we're aware of have yet announced support for the product.