So over the last month this crack has appeared on my armrest. It's not just a simple split going one way -- it's shaped like an H. On close inspection, it appears there was some kind of repair there before.

Is this worth even trying to repair with a kit, or should I look for a good used armrest to replace it with?

 

Repaired once before, break the cycle, replace.

 

A good upholsterer will fix that, but get it redone with pleather. Mine was done 10 yrs ago and is still in great shape. Pleather is softer, more durable and cheaper and you can't tell the difference. Shouldn't cost much more than $150-175 if you get the cup holders done if needed? I would say $75-100 for just the pleather.
Now there's always the eBay option, I've seen them from $60-100. But you don't know what your getting.....just saying.

As you can see, its almost impossible to see the difference. There were subtle shade differences throughout the car until I had it dyed, but the center council wasn't touched. I also had the emergency brake cloth replaced at the same time as the headliner roughly 9 yrs back...