too till or not too till?

Though moot in my case, Ive done done it, when planting a new lawn be it seed or turf shall one rototill?
I did it because it facilitated some leveling and I just pretty much tilled our old lawn under. not so easy as one would think. Had I been more patient I was going to cover it with landscapers cloth for a month and say adios to most old weeds. Fortunately I did this in fall here in Central California and the drought and our not watering for some time in advance had anhilated most of the weeds and lawn.We have super rich black topsoil that seems to go down forever.
The question really is, is rototiller actually generally a bad practive because it disturbs the most lively top layer and the worms, etc. as I have been reading elsewhere, and specifically should it be avoided when preparing to install sod/ seed a lawn?

If you have great soil, I would want to avoid tilling.  While the following statement is not exactly true, the truth could fill several books, so think of this as a sort of general rule of thumb:  every time you till, 30% of your organic matter is released into the atmosphere.

If you have lifeless dirt, tilling can be a good option.  Especially if you are tilling OM in!

thanks