I've seen it happen, but never 'as is'. I've been playing a Changeling who has it as a minor action racial power, and even then, I ussually use it because it let's me get an extra shroud as well.
As a standard action? I see no reason why it shouldn't be at-will basically. Now, there are of course some feats and paragon paths, etc that modify it. Once it gives you a free basic attack (so it's at least comparable to a standard action) and giving combat advantage to everyone, etc ...it becomes something people might actually use, and not necessarily something that should be at-will.
But really, on the one hand, making it at-will won't break it ... then again, I don't know how often someone would try to use it more than once per encounter. It's not that people aren't using it because they are saving it for later ...