It is not a bug. I got into a discussion with Ton and Martin (theeth) and it´s actually working as intended.
If you press <e> to extrude, you are initially constrained. There are 3 modes of constraining in extruding.
off - global axis - user selected axis
When extruding an edge or two vertices, the user selected orientation is replaced with normal orientation and transformation is constrained to the plane perpendicular to that edge (locking normal Z), as such, it’s now at the “user selected axis” step in the cycle.
The constraint for <g> grab/move works different though. If you want it to work like you (and I) would expect it, you got to use “extude+move”. Press spacebar to bring up the menu and type “extrude” and see your options.
I don´t know where I would prefer a normal extrude over an extrude without a move, but as I posted in the tracker I never ran into it, but might at one point, because I usually cancel extrude with the right button and then <g>rab the new geometry and translate it into place.
Here´s my being slow on the uptake in the full version: