It was terrible because you could get all 3 choices in a lowercase usage (s, ss, ß) and then lose that distinction when capitalizing. You couldn't reliably uncapitalize such words unless somebody disobeyed the rules by leaving the ß unmolested.
Lingering affects will be with us for ages, for example in the rules that computers use to do sorting and searching. The default capitalization rules for Unicode can't really change because that would break somebody's database or filesystem.
It is a real pain for Spaniards living abroad. It is not a middle name, a two worded last name, or anything of that sort. Full legal name = First name + Parent A's 1st last name + Parent B's 1st last name.
Edit : As pointed out in another comment, a Spanish last name can be a two worded one, and a first name can be as well, and often is. So you could end up with for instance, a 5-word nightmarish José Carlos ( 1st name ) García ( 1st last name ) De Maestre ( 2nd last name ).
It's two last names, father and mother first last names. I guess the same definition works, but it's worth noting that any last name might contain a space.
I started spelling it "Dealmeida" to avoid confusion.
Names are fun. I recently had dealings with a company that assumed in its employee roster that the last word entered in the name field was your last name (i.e. anything beyond the last space). One of my coworkers was from Spain and had a last name consisting of two words separated by a space. She was the very definition of a failure case for that system.