It would be nice if you could craft a rope item from vines that act as a ladder that could be hung from a roof or whatever. It could use the collision box of a single fence, just stacked many times. It would be difficult to climb but I guess that would just be a risk vs. reward situation.
So basically, vines are just a retexture of ladders that generate naturally?
If they have no collision box then they will be rather different, but yes, a similar function will be shared by both.
At first glance it seems unbalanced, free ladders and all, but if Jeb does what we think he will do he will make vines be the one without the collision box. That means ladders will still be the better choice for construction, as they can be collected without a tool (shears) and also can be stood on and not enable the "suspended" tax for destroying blocks like when under-water.
So, while vines are plentiful, you still need shears, iron, wood, etc. to obtain them. Essentially, vines are tier after ladders with less use. The only real benefit they have over ladders is that they grow, so you just have to plop one down a shaft and wait a bit instead of spending 256+ wood to make ladders. So, vines may be a tier above ladders yet with less use, but they are cheaper if you are patient enough.
Only thing I'm wondering about is whether they will grow the MASSIVE trees or just the single block wide, slightly taller than normal trees... (they are the same shape as swamp trees, just a little taller)
If you can grow the huge ones with one sapling then wood will never be an issue... I think they should take 4 saplings in a square formation. Makes sense given they are 2x2 trunks!