A second tuner is important. I can assure you that you will find yourself wanting it.
I can see it as a nice feature. And there may come a day that I have two shows that conflict and neither of them are being re-aired within the next week. But I see that as a rare enough occurrence that I may not want to go for the DirecTV TiVo. I'm pretty sure I know what I want.

As of yet, though, I'm still undecided.