Just started a new binder in a friend's campaign (Eberron; valenar elf, aiming to multi-class into wizard and eventually Anima Mage prestige class). It has turned out surprisingly well. 25 point buy, so I'm running a 12 Cha and no feats to improve my pact-making ability. That means most of the time I'm going to be making "bad pacts". Far from being a drawback, it provides a great opportunity for some roleplaying (...and some truly erratic behavior). The other players are so far taking it in stride, although they're somewhat confused why some days my elf has a deep growling voice, other days I'm contributing generously to dwarven beggars, and other days I'm refusing all food and drinks offered to me.
Mechanically, the class seems both sound and valuable (...unlike, say, the truenamer...). Although I built the character with Leraje in mind at 1st level (various archery abilities), I actually found myself binding Naberius and Aym most often. Naberius was invaluable for city-based adventuring (Diplomacy, using Knowledge skills untrained, Command), while Aym saved my bacon more times than I can count in a dungeon crawl. With a bit of research, the party found out we would be encountering a lot of vermin, particularly swarms. Aym's fire aura proved an effective deterrant, and the fire touch ability was invaluable when we ran into a few opponents with massive natural armor bonuses. I can also see myself getting a lot of use from Ronove as well, particularly at higher levels. The wind blast feature, movement bonuses, and Feather Fall at will is pretty decent.
It might still be the "honeymoon" period for me, but I'm currently so fond of the class I'd likely create another binder if my current one met an unfortunate end. Perhaps a human binder with more Str and Con, go more melee-oriented, prestige into Knight of the Sacred Seal. Hmmm....