You will get better answers at offical SESI forum for UE4 HEngine implementation.
Houdini, like UE4 and any other software that is owned by private company, not by evil corporation, has very strong community managed by company itself, with very good contact between developers and community. So if you are looking for some Houdini info go to Side Effects forums or to odForce forum, which is also frequently visited by Side Effects developers.
Yes, we are using it.
Is it worth it? Ask Microsoft, which AFAIK worked (works?) closely with Side Effects to implement HEngine in UE4. It seems that they are happy with it.
Here is one of the recent examples how companies use Houdini in their game pipelines.
BTW. Make sure to check my Houdini tools on Orbolt shop (link in my signature). You may find there some functionality that will help you smooth transition when jumping off from other apps. And follow me on my Vimeo and Twitter (links in my signature) 