Been using this for about a week now - I highly recommend taking a foto of your teeth on day 1 for comparison.By day 4 - I noticed a difference and took a foto for comparison and definitely my teeth were lighter. Full disclosure- I drink 3-4 cups of coffee a day, often smoke a cigar once a day, and drink some decaf chill out tea at night. So my teeth have a lot of room for color improvement.Today will be day 7 and I will take another foto for reference. Sorry, I'm not posting the pics, I really don't like the look of my teeth since they've gotten a bit crooked over the years.I also recommend that you dry your teeth a little before applying the strips and use your nail to press the strips into the little spaces your teeth might have.I don't notice any taste that is "bad". Basically just dentist type stuff that is sticky.30 minutes goes by really fast, and then 5 minutes with the light is also over before you know it. Then taking the strips off can require a little bit of focus. They stick really well if you apply them into dry teeth.As for gum pain, I noticed a little irritation on day 3 then just adjusted the strip placement as i realized i had part of the strips covering my gum and that solved the problem. Since then, no issues.So far I really like this product and I'm looking forward to seeing my teeth at the end of next week.