I have read extensively about Lowlines and they seem to have a lot to offer. This is the first I've heard about temperament problems. I have also read that they tend to have poor feet and legs although great progress has been made in that area. Their strengths are more pounds of meat per acre, great marbling on grass alone, and huge rib eyes; they often have rib eyes as large as full size Angus. They are actually purer that mainstream Angus but not accepted by AAA. They are registered with American Lowline Registry and now by the newly formed "Midline Angus Association" which encourages matings with Native Origin Aberdeen Angus ( Pure Angus descendants from the original cattle from Scotland). Red Lowlines are accepted in the USA associations but not in the Australian one--separate registry there for reds.
Personally I would not cross them with anything. They are the perfect size to fill a yuppie's freezer and, if kept pure, can be sold as breeding stock to other direct marketers or hobby farmers. Also great for 4-H projects, etc.