In Austin, there is a section of McNeil Road between 183 and Parmer Lane with neither a bike lane nor a shoulder. It has heavy vehicle traffic, including, today, me. As I passed a cyclist I could tell he was distressed (mainly by the shoulder-shudder and lack of visible neck) as cars and trucks whizzed by his ear. All of this, in my mind, was unnecessary.
There was a perfectly good, unused, middle turn lane available. When I travel this section, that is where I ride and for the most part, have had zero problems. I do the same on a section of road in Round Rock (University), and several other areas where I ride. Even when traveling the country, if the middle lane is the safest option, I have no trouble opting to take it.
To me, it makes perfect sense. Rather than have the driver behind you slow down and worry about giving you enough room, or worse, not slow down nor give you sufficient clearance, just move to the middle and let the cars have both lanes. If the occasional vehicle wants to make a turn, it will be slowing anyhow, and it is my opinion they will be more likely to see you, since you should be right in front of them.
As for oncoming traffic who will be turning left, you have several options. Since you can see oncoming cars, if the lane on your left is free, you can just drift into that lane until past the turning car. If the lane behind you is clear, you can drift right, giving you the right of way. Of course, just because you have the right of way doesn't mean you'll get it, but, once again, you should be right in front of his windshield and pretty much know if that is a good option. Of course, you can always stop and let things clear. All of these options, in my opinion, are better than sharing a lane with a vehicle.