It's been challenging for sure in this soft(ish) regolith and the slope angle.

It also looks like there was a failed drive on sol 1287. After losing Spirit rover in a sand trap the rover drivers have been very careful traversing across loose sand.

I would not be surprised if they make a move to either side of this 'smooth passage'. The orbital imagery appears to show more favourable terrain (rougher) at the north and south edges. That diversion may only be required for the next 300 meters or so, as the distance between the contours widens a little after that, before narrowing again as they get nearer the rim crest. Whichever path they take it's going to take a lot of drives to reach the crest.

It was a huge challenge. There's a really good video out there on the challenges the team faced. I'll see if I can find it, but if anyone else has the link please share it here :)