Hmm..
I was practicing it tonight when the server was pretty much empty.
Just me against one completly new player who did nothing on marines but build turrets.
Found out that there is a certain amount of time alright before it blows.
Getting it right though... thats a different story.
Also i noticed that you can leap and bite *after* enabeling xenocide, which is pretty damn handy getting close in time.
Found myself activating it around a corner, waiting two seconds, then going around the corner, leaping and it normally explodes right on contact of where you aim.
Had a good few laughs with it alright.
God i love it.
Must get a script going where i say KAMAKAZE! everytime i activate xenocide