I did some tests with the new "spring2" constraints in Blender 2.79 master in order to make them work for our BCB add-on development and I noticed a serious instability issue with them. In larger structures with high stiffness and damping they cause strong jittering and explosion effects. And when stiffness and damping is reduced enough so that they don't explode, they are already too weak to keep something in place. This wasn't the case with the former springs.
This .blend file contains a structure with springs, which will show a slow deformation behavior in the latest official Blender 2.79 release. The same file simulated in 2.79 master branch, however, will make everything explode instead. You can reduce the stiffness to something like 10,000, then it only jitters but at the same time it looks like nothing is connected anymore.
I couldn't find an actual advantage over the old springs, which at least were stable at all times. In case this is not considered a bug, I'd ask to make the spring type optional at least to offer the user a way around this limitation.