This was a new unit....it didn't replace anything? Anyway...we had a crack at some rules based on how it looked. It is designed to drop 6 full transports (hence 18/6 vehicles). I doubt it would make a huge difference to anyone if you "errata'd" the save to 1+....but 3+, Superheavy, 2 Void shields seemed pretty representative to me...I doubt it'd have the armour of a Baneblade. I'm also not really worried that you could drop 6 full Landraiders....but again if you don't like don't let it happen
I use Teleporting and Deepstriking units a bit. I find psychologically it is awesome....your opponent will often go out of their way to kill the Deepstriking units..often using weapons systems that would be far more effective shooting something else. In my last game my opponent (hope he doesn't read

) wasted the entire fire of a Leviathan trying to kill a detachment of Swooping Hawks. If you don't use them early, they can also be great as your opponent will constantly be worried about where they might turn up.
Generally, the most profitable time to drop them is turn 1 when you know there wont be many units on first fire. It's usually a good idea to go really deep too so you get out of fire arcs of most units (for normal shooting). Alternatively they are also great late game to reinforce a particular area or to snatch an unguarded objective.