Right - a Star Pact warlock is always going to take the power (usually encounter or daily) that gives him the star pact bonus. Same for Infernal and Fey too. You just don't take anything else.
Speak for yourself. I have. Especially when the other options are nicer than your pact one. Or they're more thematically appropriate (with a little fluff adjustment). Or you're an Infernal warlock who wants to do something more than just Fire. Or a new pact comes out and you nab a power from it.
In many cases the boost you get from your pact is just so fiddly that it's not
that much of an incentive to grab that power. For instance, Fiery Bolt. Adjacent enemies to your initial target take 1d6+Con damage. If you're Infernal and you take the power, it does 1d6+Con+Int. That's not
that great of an extra benefit. Not enough, imho, for me to feel like I have no other choice but to get it. Same with Otherwind Stride; the benefit is that instead of teleporting 5, you teleport 5+Int. That's not a benefit so significant it makes it a no-brainer. Same with Mire of the Mind; the pact boon is a bonus to stealth for the encounter.
In fact, there's specific rods for Warlocks that grant you the pact-benefit of a power, even if you don't have that pact. (I.e. you're a feylock with a starlock power, the rod grants you the starlock pact benefit for that power).
And, dailies do not grant pact benefits. So you really do have the choice of dailies.
The only thing that feels restraining, IMHO, is that the powers' primary attacks are different ability scores. A Feylock's primary is Charisma, an Infernal is Con, a Starlock can go Con or Cha. So the Infernal Warlock has only to choose from the Infernal and Con-based Starpact powers, etc, because it is unlikely his Cha is going to be big enough to make the non-Con attack powers a viable choice.