It ruins the beautiful landscape. However, it totally screws up the 1UPT. If Firaxis is set on keeping 1UPT, they should at least get rid of road maintenance.
In Civ5 there is a strategic tradeoff between having more movement flexibility in your territory and paying more gold.
How are strategic tradeoffs a bad thing that need to be removed?
A Civ design should always first begin with the design of the builder game, and only then add on the design of the military game as an extension of the core game.
I disagree with this, I don't think the two can be separated, particularly in a 1upt environment. 1upt means there need to be fewer units overall, which means unit construction times need to be longer, which affects what building times should be, what tile yields should be, what tech costs should be, etc.
For all the people complaining about aggressive AIs attacking you, I think there's also another point which should be obvious but seems too often to be missed: warfare is basically the only manner in which the AI poses a threat to the human player, and actually frustrates your attempt to win.
Everything in the game basically ends up mattering strategically in a competitive sense in terms of how it affects your military. Tech matters because it allows more advanced military units and things that buff your economy, and economy matters because it allows you to build more military units, build more structures that buff your economy or your military or research more tech - for more military. Social policies matter because they either buff military directly, or improve your economy.
There are a few exceptions (and are more exceptions in Civ5 than in Civ4, with city states for example), but this is basically true, and has been basically true in every game in the Civ series, and is true in basically every 4X strategy game.
If the AI isn't aggressive, particularly when you're weak, then you can basically ignore it, and focus on infrastructure, under-investing in the short-term in military, which lets you grow economy more instead, which lets you have a larger/better military in the long-term, which lets you conquer the AIs.
Complaining about AI aggression is a lot like complaining about rushes in an RTS game; without rushes, there is nothing that makes teching a risky strategy.
Now, there are all kinds of reasons to complain about weakness of the tactical AI, and that the tactical AI is too aggressive, and so forth, but I don't think that military and warfare is something that you can or should try to separate out from the game as an afterthought, since it is integral with how the AI players interact with and frustrate the human's attempts to win.