Horseback archer is solidly ho hum. He's a bit expensive, but ranged is always nice. Mostly superceded by marksman of lorien, trollshaw scout, and Galadhon archer, he hasn't seen much recent play. But if you want a ranged attacker in a Rohan deck, he's pretty good.
Core Set #30. Tactics.
Horseback Archer is one of the better archetype of ranged allies in the core set. First of all, he got 2hp and , so he can stand for more then round, and also he got rohan trait, which makes him ideal for rohan deck, which was quite supported since the first adventure packs cycle. Quite good artwork also. Verdict: 4/5.