I was fiddling around with various builds in the DDI CB, and noticed something odd with its retraining behavior in a particular situation. Then I took a closer look at the rules elements that had led to that particular outcome, and realized that by RAW it was technically behaving correctly...
Guess what you now have? A 1st-level Warlock encounter power. Which can be retrained to a different 1st-level Warlock encounter power. This is different from all other power-granting multiclass feats, that say "you can use that power once per encounter", and which the CB treats as you'd expect. I expect them to errata this, but in the meantime, enjoy your bonus warlock encounter attack at the cost of a single feat.Binding Initiate [Multiclass Warlock] Benefit: You gain training in one skill from the binder warlock’s class skills list. You also gain proficiency with rods and wands. Choose a binder pact boon. You gain the at-will attack power and the utility power it grants at 1st level as encounter powers.