Thanks for all of the replies everyone. I don't fancy crashing because of this. The wear distribution is indeed poor and I'm not sure if it's because of the old brake pads, which I've since replaced. I have a set of Mitutoyo calipers that I'll use to measure the rim width. If all looks good then I'll try sanding down the track to improve the cosmetics.

With regards to rim wear, other than wall width and looking for a concave track, what else have you guys noticed on rims that are about to go bad?