Previous manned spaceflight vehicles, that had a Launch Escape System (Excluding you space shuttle!) usually seemed to favor the notion of a tractor (Puller) style LES.
That is, the manned module is at the top of the stack, there is a motor (often in a tower) that contains solid or liquid engines for an abort, to drag the manned module away from the stack in times of woe.
With the newcomers to the manned space business (SpaceX, SNC, Blue Origin) and the old school approaches (Boeing and Lockheed Martin) we start to see different approaches, where SpaceX (DragonRider), Boeing (CST-100), SNC (Dream Chaser), and Blue Origin (SV? Darned if anyone knows what they plan to call it. New Sheppard is the sub orbital vehicle name, and Space Vehicle, SV is the current name I last saw for their orbital version) are working towards the idea of pusher escape systems.
NASA with Mercury, Apollo, and now Orion seem to favor tractor LES.
New guys are seeming to favor pusher systems.
Soviets have used tractor systems for Soyuz, and while some of the fun proposals in Anatoly Zak's book suggested pusher systems, none of those have really seen the light of day (Looking at you Klipper, NPK-TP, etc). What is neat is that even though the manned module is the middle of three in Soyuz, they still went with the tractor system.
Chinese with Shenzou seem to have gone with tractor systems as well.
Are there examples of actually flown hardware, using pusher escape systems, or will the new guys be the first, assuming any of them actually get to launching a manned system? (I hope they all succeed, but who knows! If you are reading this in 2020 and in hindsight laughing at my naivete, please enjoy).