Until today I've been under the impression that it is not possible to control the "orientation" (i.e., the horizontal and vertical directions) of a created plane. In the rare situations where you need a particular orientation, you can jump through hoops with the align grid/origin command, but generally it just isn't worth it to get a vertical or horizontal sketch relation to mean what you want.
Today I discovered that if you construct the plane such that it is
- coincident to a sketch line and
- perpendicular to a plane or surface that is not normal to that sketch line, but is normal to the desired plane
then you'll get a plane whose horizontal direction is the direction of sketch line. If you then sketch on the newly created plane, the "left" side of your sketch will be the side corresponding to the first of the two points involved when you created the sketch line.
In the picture below, Plane1 is coincident with the Front plane, but is oriented such that the horizontal direction is 25 degrees counter clockwise from the X axis. This plane was created as being coincident to the line in the visible sketch, and perpendicular to the top plane.
It is necessary that the plane that is used for the perpendicular reference not be itself perpendicular to the sketch line. For example, if rather than use the top (or right) plane for the second construction reference, I use the plane highlighted in blue in this next image, the feature will fail.
Hope this helps somebody out. I don't need this often, but it will come in handy for me.