The abilities of the class are decent. You get a competence bonus to social skills, telepathy and you get a slave at level 15(if you can meet the skill prereq by level 5). The problem with the class is that most of it's class abilities are based on existing spell. Warlocks may benefit more than Wizards and Sorcerers, they can more easily meet the prereqs too(Bluff, Intimidate and Sense Motive are class skills), but they don't meet them until level 6. If you're taking it as a Sorcerer or Wizard, you lose the last 5 levels of spell progression, which means no 8th or 9th level spells for Sorcerers and 1 8th level spell for Wizards. If you take it as a Warlock, you lose 3 dark invocations and 2d6 damage to the eldritch blast, along with fiendish resilience, 3 points of DR and Imbue Item. Though eternal charm is useless for a warlock and beguiling influence makes up for the 2nd level skill boost.
As far as rollplaying is concerned, there are better alternatives. You could increase the spell progression to 7-8/10 and keep all the class abilities. None of them are really powerful enough to justify a 5/10 progression.