I found them to be rather peaceful... It was a rush whenever I ran out of time or stepped in water and woke up the guardians, but other than that... they weren't creepy at all. If it wasn't for the fact that the guardians rushed after you, I thought it was extremely peaceful. I seriously would have walked around and enjoyed the serenity if I wasn't timed.
It did feel like a part of Silent Hill. However I love creepy and odd things in Zelda games, that's why the Silent Realm goes up in one my favorite things in the whole Zelda Series. I will say though if you are a person who gets scared from watching horror movies that are only a little bit scary or you are under the age of ten. Prepare to have nightmares!
I actually never had a problem running out of time, but I have accidentally stepped in water and intentionally got caught by poes (for more of a straight shot to a goal) a few times. Never actually got hit by anything, which is amazing, because a couple times I was right next to a flying guardian (one being at the top of the lighthouse, it somehow missed).
No way, they were awesome. Stressful, yes. Freaky, sure. Heartbeat went to whole new levels, why indeed. But Silent Realms really livened up the game, it had been pretty peaceful. Though I never had problems with time either. It was more like...getting caught by a Watcher or accidentally walking/sliding into cursed water.
The peaceful atmosphere when you entered the realm plus that tranquil music was just right - a false sense of security, which disappeared quite fast. It worked - that's what really matters. It wasn't "will give you nightmares" -scary, just refreshingly different from everything else.
I really liked them. Sure, the Guardians (especially the ones that could float and had the giant machetes) were a little eerie, but it was more of a heart-pounding place than a creepy one. It was a really good way to implement a stealth aspect in the game while still having us charge straight forward due to the time limit between each tear. I really liked them.
I thought they were pretty awesome myself. A little tense and stressful when you ran out of time/stepped in the water stuff/got detected by the watchers, especially because you knew you'd have to start all over again if you got hit. It wasn't really all that hard; I think I only got hit twice, that because of making stupid mistakes getting to the very first tear in one of the realms. I never really found them creepy either; but then, I just recently was introduced to the Resident Evil series, and compared to that, the silent realms are positively peaceful and serene (which they actually are, until you're caught).
That says what I believe. I didn't find them the least bit scary, really I found them to be a massive upgrade of the TP Tears of Light, and THOSE weren't scary. The music wasn't really forboding to me as it was "watch your back" [to me, foreboding means something terrifying is drawing near, whereas "watch your back" just means stay alert].
blackice_cc actually brings something up – the Guardian Chase music actually reminded me of the Resident Evil series. And while I realize the "scare" in both series are of completely different nature, Skyward Sword somehow seemed to try to reach over into RE and grab some of that feel, what with the bizarre enemies, searchlights as well as 'assertive' music.
So no, I don't think the Silent Realms were scary, but DEFINITELY fun.
I thought they were awesome. The music that played when you were being chased by the guardians was great and really set the mood to make it feel like something was around every corner and if you stopped you wouldn't survive. I personally loved them because they were unique and special.
altogether I liked them; they posed a decent challenge, and you got a useful item out of them. The weren't really scary though, just a bit unnerving in the challenge posed when you're first faced with them (they want me to do WHAT without my sword?! have you seen that guy, he's HUGE!). Much better than the tears of light.