About transactional memory: I know that software TM has 2-4x performance overhead, but hardware can eliminate that. I've been working on hardware transactional memory design, and I can say with some authority: if chip-makers add proper HTM, and the software compilers and runtime environments use it in a non-braindead way, transactional memory will run at greasy fast speed. Faster than locks, usually. It's going to be great.

For example, did you know that you can get a highly scalable priority queue data structure by just using a skip list and hardware transactional memory? It's so simple that I felt almost ripped off when I realized how much easier TM makes it. If you've ever tried to make a concurrent priority queue with locks or compare-and-swap primitives, you'll be pleasantly surprised by how much easier it could have been if only we had hardware transactional memory.