Personally, I have a lot of use for the channelling even as it is now since I do remove excessive pieces of landscape or even some entire hills: Dig out the level below and cut it of, and presto! one overhang less.
In addition, I was always reluctant about moat defenses because they do not give you protection against ranged weapons which were very deadly until now - built walls did a much better job at directing people to your traps.
Likewise, I do alot of heavy landscaping, although I've been wary about the collapse method after a minor accident breached a chunk of my fort(oddly, I only ever seem to have small accidents) - the new channeling is handy for mass designating large areas without worrying that you'll overlook a tree or a sapling will grow into a tree while the mining is under way, and hazard my legendary miners with collapse-induced injury.
Still, I'd support restoring the old channeling and keeping the new as 'dig downward ramp' or the ilk.
And while built walls are ideal, they take a while, especially if you want to enclose a large area, or have dangerous critters on your map(tho at times I've brought wood and threw up a temporary palisade - wood walls seem to go up alot faster than stone). The ditch is then subsequently handy for assorted traps, a nice aesthetic moat, or just keeping enemies from hiding from archers atop the wall in that little blind spot.
In my latest fort, while landscaping, I actually left a one-tile wall of dirt/stone a few tiles back from the edge, and used that for most of my perimeter - took a fraction of the time.
Wolfius: As Zakastra hinted, removing ramps has been in 3D for a long time. It has been a standard part of my defenses to remove all natural ramps so as to force enemies to path through a few trap-ridden pathways (although you never were and still are not allowed to remove ramps at the border of the map (T_T)
Deathworks
...I've always resorted to channeling to make cliffs or building over free-standing ramps...
Wolfus Cancels : Post Topic, Tantruming