I like the look of planetary terrain. I appreciate that a moon like Io will qualify as Mountain rather than Barren.
In terms of sci-fi tropes for terrain, the only one that jumps out at me as missing are frozen-ocean and quasi-frozen-ocean planets, like Europa.
It also makes me wonder if system generation applies a tidal heating tectonics bonus or somesuch to planets.
Will the terrain system play into colonization or colony cost at all? It might also be a good way of assigning trade goods. For example, a Jungle planet could have medicinal plants, exotic animals, w/e.
P.S. - are 'Forested Rift Valley' etc. supposed to have a lower tectonics minimum than regular rift valleys?