For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Jesus could not have told the man next to him that was being crucified that he would be with Jesus in Paradise that day {today] because he was soon to die and be buried and was not resurrected until three days later!!! He said to the man "I tell you today, you will [future, at the time of the resurrection of all the saints] you will be with me in Paradise. The translators put the comma in the wrong place. There were no commas in the original Greek, in fact the Greek was written lower case with no upper case in it's written record!
As much as the comma (which you are right is a far later addition) is debated, it probably doesn't matter for the sake of what Jesus actually meant. 'TODAY' was a well understood rabbinical concept referencing the coming of the Messiah and the entrance into eternal life. Basically, Jesus was saying, 'TODAY' has come. I am the Messiah. You will be with me in Paradise.'
Question: What did Jesus mean when He said, 'Today you will be with me in paradise'?
See Answer: http://ebible.com/answers/19855?ori=167400
I agree interpreting it as Jesus saying that the thief and Himself would somehow be hanging in in Paradise that very same Earthly day doesn't make sense with other scripture that shows Jesus did not ascend to His Father until after His resurrection.