I would buy used for no more than $800. More than that, you're too close to retail, and you may as well buy new at that point! The new leathers look shinier, but I have to say, the ones that I've seen that are broken-in, the leather is quite nice as well.
New – not all new bags have thin shiny leather – the current batch seems to be much nicer and thicker than SS06. The other problem I have with black bags is that any handle darkening cannot be seen. You could be getting really gross handles and touching someone else's oils without knowing it. The ick factor really puts me off used bags in dark colours.
OK, I say new because not all the newer (06 and 07) leathers are "bad". Just call BalNY and explain exactly what you want as far as the look and feel of the leather. A black first is something they will always have tons to choose from (since they make it each season) and they can hand pick one that fits your leather preferences. It's shouldn't be hard finding a good one and then you'll enjoy the smell and ownership of your very first brand new Bbag!