[DarkShikari]

The meaning of 2x real-time, of course, depends entirely on the resolution.

x264 now has encoding presets you can use to trade off speed for compression: they go from "ultrafast" to "placebo" (full list in the help). Grab the latest from x264.nl; we've also had a lot of speed improvements lately ;).

Do note that at high speeds, it's easy to get bottlenecked: the most common case is the decoding of the input, which is often only single-threaded. If your input is uncompressed, then you can get bottlenecked by reading it off the disk. And if you're running filters on the input (e.g. resizing it), that can also serve as a bottleneck.