The wiki says you need rollers if you're going uphill, otherwise the cart will roll over whoever is trying to push it uphill. Or at least, that seems to be what it's implying. Is that the case?
No, I believe you may have misread the wiki information, or the wiki information was poorly written. From the wiki, "A minecart set to be guided is not affected by rollers at all". It also says "dwarves can not push nor ride an unpowered cart up a ramp.. [snip].. To solve this, the player can either use Rollers (see below) or set the cart to be Guided."
Some further comments of mine on your thoughts:
So I think I've got what enjoyment I could out of this version of DF, and am going to take another break from it and wait for the next major version. Some things I would like to comment on:
Burrows: Getting dwarves not to go places is still a nightmare and the one of fastest ways to lose interest in playing dwarf mode. Haulers sometimes seem to not even pay attention to burrow restrictions, actually leaving the burrow and going outside during sieges, even after all items I could find outside were forbidden. Again, it would be great to have a forbidden area traffic zone that actually forbids dwarves from going somewhere instead of increasing the pathfinding cost, as if there's a wall. Burrows have been suggested for this purpose, but as demonstrated here, they don't work nearly well enough.
I've found that using the military alert screen to work better for the purposes of corralling civilians into safe areas. [keystrokes: (m)ilitary -> (a)lerts -> select active/training schedule -> select burrow] Once a good burrow system has been set up to work with military alerts, there is very little that can go wrong [at least, in my fort so far, this setup hasn't failed].
Stone drop rate: Love that stockpiles are usable upon mining them out now, but mining out entire limestone mountains to make enough steel for the army seems like it needs adjustment.
I reckon one fix for this would be to mod the raws to allow flux stone blocks to be used in smelting. On a (somewhat) related note, somebody here modded their raws to allow tin bars to be used for glazing stonewares instead of cassiterite ore after the drop rate had been changed.