I was very impressed when I first tried them.. usually I feel some irritation when I sing, especially for long periods. But after taking one of the voice gums, there's no irritation at all. It just feels smooth and comfortable.
Being a coffee drinker doesn't help. Coffee is pretty bad for singing. I've cut down to 1 coffee per day, and I drink water afterwards to re-hydrate. I don't drink coffee on the day I have singing lessons either.