This is the default on latest CatOS release, but not yet on IOS (it's on its way though). You can enable Rapid-PVST by just setting the mode (spanning-tree mode rapid-pvst). Note that you can also run an IEEE-like RSTP, with only one instance, by using the mst mode with no configuration.
it does make a differnce over STP as the algorithms are more efficient to allow for more rapid spanningTree convergence in the event of a topology change. (quicker network recovery than with normal stp)
CatOS is used in some of the 'higher' end switches but is starting to be phased out for IOS Switch versions. (helping to keep all cisco OS versions more similar)
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...