Lorna Mitchell has posted some preliminary PHP7 benchmarks from the current alpha release (alpha2). Good news - it's fast....very fast.

If you know anything at all about PHP7, you probably know it's fast. But did you know how fast? The alpha is out and looks very robust, so I decided I would create a new set of benchmarks to include it. Graphs first, disclaimers later :)

This graph shows the time it takes for each version of PHP to perform the same task, on average, with oldest PHP on the left and moving forward in time. [..] The benchmark is the Zend/bench.php that lives in the PHP sourcecode (run ten times for each version of PHP using the php7dev VM on an average laptop, and then the mean result for each version calculated). The script runs through a series of taxing algorithms, giving a sense of how quickly a series of computational instructions can be executed.

She also talks briefly about how this can effect more real-world applications, how realistic it is to upgrade from older installs (much less painful on 5.5 or 5.6) and some things you can do to help improve PHP7 for everyone. This includes testing, working on bugs and adding extensions to this list to ensure they're made PHP7 compatible.