Aluminium's right - layer breaks on BD-R DLs are no problem at all. There no longer needs to be a conscious decision about the layer break position - I regularly burn ~25GB video files to BD-Rs (usually as part of a playlist with other items) and the data simply flows onto the second layer when the break point is arrived at. Likewise, playback should be seamless - BD player buffers are much more effective (as, I suspect, are the laser mechanisms).

Of course, the real issue (as you suggest yourself) is compatibility: you need a good burner, good burning app, good discs AND a friendly player at the receiving end. Still, let's not let caution stand in the way of a quality product...