So what I gather from all of this discussion is:
The panther is a late game high-end tank destroyer with high cost and excellent mobility.
but it sucks at destroying tanks and if it's using it's high mobility it won't hit anything.
I've almost completely given up on Panthers. The Jagdpanzer seems to always be a much better choice or Stugs as Ost.
For me it largely depends on the map. If the map provides lots of flanking opportunities than the panther is the right choice, even despite its downfalls. Even if you don't plan to flank with it immediately you can use it as a skirmisher and fast flank the SU85s/Katushas/Caliopes (or what ever) when the opportunity comes up. However if we are talking maps with serious choke points than always prefer to stick with PAKs and or Jagdpanzers/Stugs to cover.
I hope with the coming tone down of the Comet the Panther will feel not so terrible any more though.