SuStel:
> Explain to me, for instance, the difference
> between ben
> puSqu' Athens vIDabtaH and ben
> puSqu' AthensvIDab. Also explain the
> difference between Hoch jaj puH DujwIj
> vISeDtaH and Hoch jaj puH DujwIj vISeD.

You're definitely right. I re-thought these sentences without the {-taH}, and there is no difference. Thanks for pointing this out !

It's not that there's no difference; it's that the version with -taH does not mean exactly what the version without it means, and it's the version without that you intend.

Hoch jaj puH DujwIj vISeDtaH means something like every day I am continuously driving my car. But continuity and being ongoing are not really what you're trying to convey. Sure, the act of driving is continuous from one moment to the next, but what you're expressing is your habit of or regularity in doing any driving at all. That's not a continuous concept. You want to tell me that your driving was a regular thing you did. There's no suffix for that. Hoch jaj puH DujwIj vISeD.

-- 
SuStel
http://trimboli.name