The only postseason event I have any experience with is the Super in '07. I bought tickets ahead of time, but I know people who drove over the Friday and Saturday mornings we played and waited for several hours in line because of the limited number of seats.
Just remember this, though...
1. That was a super regional against Clemson... a big name opponent... and it was for a trip to Omaha...
2. LT was still AD, so there was a cutoff of about 13.5M in attendance
3. LT sucks... and everyone who didn't get a ticket got to go to the Hump
I think you'll be fine waiting... but I'd buy Saturday tickets ahead of time. If people are going to travel for a game, it will be that one.