Ilfosol-s doesn't work well with fast films, I'd only recommend it for 100 ISO and slower emulsions.(posted 8223 days ago)
As John says, it introduces a noticeable shoulder on most films, and for this reason it's particularly useful with T-max and Delta 100. The little bit of extra grain it gives on these films is a reasonable trade-off, IMHO, for more printable highlights and a slight improvement in sharpness over D-76. It works reasonably well with FP4plus, too.