jjpixelc Is there no bone "snapping" in Spine?

There is not snapping to a parent bone, sorry. To place a bone at the parent tip, set the local translation X to <parent bone length> and translation Y to 0. Be sure to choose the Local axes first.

Some software requires a child bone to be at the parent bone tip, but being able to place the child bone anywhere provides more flexibility. In practice with Spine, placing a child at the parent tip is often it is not needed. Also bone length is mostly a visual aid for the animator, there are only a few things in Spine that make use of it (IK and path constraints).

If you want to create a new bone at the parent tip, click the parent bone, then with the Local or Parent axes selected, click New > Bone.

If you want to create an IK constraint target at the tip of a bone, when choosing the target bone you can click the child IK bone to create a new target bone at the tip.

jjpixelc Is there a way to grab the connection point of parent/child bones and drag this, thereby manipulating both bones, instead of having to manually adjust both of them?

In setup mode with the rotate, translate, scale, or shear tools, you can drag the tip of a bone to change the bone length. You can hold alt while doing this to also move the child bones.

jjpixelc In general, I must say I find bone creation and adjustment a bit of a bother and more time-consuming in Spine compared to Mecanim due to the fact that manipulation is locked to various types and axes instead of being more "free-form" like in Mecanim.

I'm not familiar with Mecanim bone manipulation. In Spine typically images are placed first, often by importing from Photoshop/etc, then bone placement is mostly about getting the origin in the right place so things rotate/scale/shear as desired.

Bone compensation may help. Click Bones, then when you manipulate bones the children are manipulated in the opposite way, so they appear not to move. The Images button does this for attachments. Be sure to turn it off when you don't need it anymore! It can be confusing when left on (the button flashes when the compensation is applied to draw attention to it being on).

Oops I missed this one:

jjpixelc is there a command to return the skeleton to the "default" pose (as it was when imported from Photoshop)?

If you are in setup mode, you are already looking at the "default" pose, since setup mode is where that is defined. There isn't a way to go back to how it was when imported from Photoshop, besides undo. You should use animate mode for trying out poses temporarily.

If you are in animate mode, the pose comes from the setup pose + animation keys. You can delete keys to get the setup pose, or create a new, empty animation. You could go to setup mode (ctrl+tab), select all bones click viewport, ctrl+A), copy (ctrl+C), go to animate mode (ctrl+tab), and paste (ctrl+V) to paste the bone transforms. This will give you the setup pose which you can then key or let auto key set keys. I don't think that is needed very often, though you may want do it for just a few bones rather than all bones.

Also you could use the Favor tool (heart icon in the graph view), show all curves for all keys in the graph, then choose Setup then drag the favor slider to the right until it is full. This sets keys to give you the setup pose, or a pose between your keyed pose and the setup pose. The favor tool is pretty neat, if somewhat advanced. The most commonly used mode is Favor.