Hunter65536: Unless their detection meter fills up completely you are safe to blink away.
Personally I enjoyed this game a lot. Did a pacifist(clean hands) playthrough. Got a bit tired at the end so my final level I just used slow time and blinked my way through while chugging mana potions.
Oh yeah I've Blink'd away many a times. While the "turn around as soon as the player is within two feet of you" mechanic is annoying, I find it equally as annoying that the guards forget about you almost immediately.
You know, I've never really EVER had to use a health potion and only used a mana potion once or twice (when I had to use an Ability that used half the bar), I never had to Blink enough times within X amount of seconds to ever get it below that first notch that it'll recharge completely from.
Anyway despite my gripes about it I do find it to be a great game. If I had to describe why I love it, I'd have to say that it's because it sort of plays (and looks) like a Batman: Arkham game where you're not stuck with the (modern) Batman's "no killing" rule. Really cool game. I'm near the end (I think?) and am looking forward to the DLC.