I played in a game that headed for a TPK. And there was no warning it was coming - we had been going through easier fights, and as a group, we were used to that general style of play. Our group of 4 3rd level character would come across the hobgoblin fighters, and we'd decimate them, taking a few hits. While there were hard times (my 1st level spellthief bumped into the BBEG - a 3rd level kobold warrior - by himself early on in the adventure, and was knocked out), the campaign generally had this "easy" feel to it.
Then, we get hit by a HUGE fight (three ogres, with a few levels in barbarian and optimized feats, vs. 4 close-range 4th level characters) that very quickly kills the group.
It was an unbalanced fight, but it was also a new GM, and we would have said something like "Hey, you misjudged the monster's strength, it happens sometims", were it not for one factor:
The GM laughed while he killed the group.
This pissed us all off, and now, we've manipulated events around our gaming table so that he doesn't get much time to GM.
So, I'm not going to say you're a bastard GM for a TPK - these things do happen. But then, I'm not at the table - If I knew how you HANDLED the TPK, things might change.
I voted for "It's low, but I'd still play" simply because I firmly believe that a TPK (unless it's early in the campaign) is typically the fault of the GM - he misjudged the playing abilities/character strengths/monster strengths of the encounter, and the whole party suffered as a result.