Why blink sentries?

If everything has blink, I would think forcefields would become relatively useless.  Blink zealots might be able to fight blink zerglings, though, since it's already a close fight without blink, and you can blink away wounded zealots far easier than blinking away zerglings.

Blink Dark Templar would be fun without being extremely over the top.  Zeratul had that power in the campaign.