The ability grants only the charmed condition and the telepathic link. Any "control" would need to come from Persuasion, Diplomacy, Intimidate, etc. which would be likely to be effective due to the permanent advantage. The target will not be able to escape checks, either, as long as he's on the same plane.
The power of the ability, then, is tied to the character's Charisma and skill proficiencies, while the target's resistance to control is linked to their various opposed skills.
Note, too, that while a charm person spell specifically ends when you attack the subject, that's not an effect of the charmed condition itself nor of Create Thrall. Create Thrall can only be ended by remove curse or until the charmed condition is specifically ended by another effect (i.e., greater restoration, hallow, power word heal, et al). Thus the Warlock is perfectly free to attack his or her Thrall and the charmed condition will not end.
Also note that charm person's secondary effects (the target perceives you as a friendly acquaintance, and knows and remembers that you charmed it) are also not present. You'll likely need to use some skills to get anything from the person, but unless you start ranting in his head he might not necessarily even know he's been charmed. Power wise, the ability is much closer to dominate person than it is to charm person.