I've extensive experience with Ranged SF (about 7 years) both as units and as militia. They're now my preferred militia if I have walls to defend.
Long ago there were definitely special abilities but I've never tracked whether any of my units have had them or what they may be (I try to play without crunching too many stats). The idea that these should only be discovered in combat has always struck me as odd - surely the trainers at the RC should know what kind of training they're providing? Letting the region owner see this information would make more sense and I'm not sure there'd be any great harm in not listing it in the recruitment page.
IME Ranged SF fight better than equivalent infantry in melee and better than equivalent archers at range. A few time I've used them in melee in skirmish formation and not been too disappointed whereas I'd expect MI or archers to be entirely useless at that point. I've not used Melee SF on their own in several years as if I'm recruiting them it's usually for an existing unit with limited recruitment options at that time. From what I recall they punch hard but their casualty rates tend to be as bad as with equivalent infantry or cavalry which makes them a costly option both in gold and time between recruitment cycles.
Overall I'd say SF work best for characters with high honour who want to pack a reasonable punch in battle but still move fast or as militia garrisons for fortified positions. They also add a nice RP touch to the game.
