I really hated them. What they do is annoy me, and stress me out, mainly cause it is so easy to screw up by mistake and lose all the work you did when you were 1 teardrop away.
I'm not a really big fan stealth missions, either. It's not technically a stealth mission but it's still trying to be one. You're on a timer, too, something that I've always loathed in video games, mainly because you have to rush through them, making more mistakes in the process. I mean, Twilight Princess didn't bother me when I had to do it, but that's cause you didn't get one-shot back to the beginning every time an enemy touched you.
It's like they tried to combine the Teardrop quest from TP, with the "don't get caught or you go back to beginning" crap from Phantom Hourglass.
I don't mind it being frantic or having to not get hit.. MUCH. Honestly, the whole section would be a hell of a lot less stressful if I didn't have that obnoxious stamina gauge. It's funny, I rarely notice the thing until I have to run like mad for whatever reason. I really think the Silent Realms could have been better if they hadn't made it a 1-hit-you-lose scenario, and given the player a couple of hits. Not the full amount of health you normally have, but say 3 hit tops.
I dunno, it just really irks me that they had something that could've been really nice and then they go and make it unenjoyable by having this forced "don't get caught" thing. It's just not the sort of gameplay element I think Zelda needs. At least in Wind Waker you could hide.
...actually, now that I think about it, if Link doesn't keep his Health or his Items as he's only there in Spirit, giving him that Stamina Gauge inside the Silent Realm makes absolutely no sense, except from a "challenge" standpoint. If they wanted to make it a challenge, they could've just left that for the Hero Mode and done without it.