[Superkid11]

Not at all. There may be minute soreness, but it is absolutely minimal if there is. I haven't had a problem all day. Nothing I've felt so far can be described as pain.
I mean sure, the process of removing them hurts, and is downright unpleasant when the adhesive is being ground off, but the pain is over after they're gone.

It does feel strange though. When rubbing your inner mouth on your teeth you may feel as if you've lost the feeling in your inner lips because you're used to them touching the rough surface of braces.

You may also look in the mirror and think your teeth are huge. It's just an optical illusion as you'll be used to seeing them with braces.

... well, this may be notable. When they fit you for a retainer they use this stuff to cast a mold, which they usually do right before you get braces too. I could tolerate it when it was done on my lower jaw, but on my upper... it's a good thing the orthodontist lady planned ahead because I just couldn't take it for very long. I actually threw up a little. Fortunately the mold was cast.
My gag reflex is very strong so this may not be a problem for you.