In response to a few of the questions above:
1. Length of interview: I do not think that your 1 hour interview is necessarily a bad sign. If you did not notice, the Tepper admissions staff is incredibly friendly. My interview last year exceeded the 30 min time slot as well, if I recall and it worked out in my favor.
2. No invite for interview yet: While they are probably getting close to the end, I did not receive a R1 interview invitation until about this time last year - and again, here I am. I would not sweat it at this time (easier said than done, I know)
Thanks for addressing point 2. Do you remember when you received the invite? - how soon before the decision date...getting anxious here since its now less than a month to go.