crest white strips premium, 7 day treatment, is great. it will take at least a couple of shades off. it's kind of annoying, though, getting those "bottom" strips to work. your gums will likely be sensitive for maybe a month afterwards, but it wasn't a big deal with me.
as far as stripping the enamel off, it doesn't. it's been proven and approved by the FDA. actually its a concentrated hydrogen peroxide solution. dental paste is partially HP.
if you want to get absolutely stellar results, get the BrightSmile treatment. it will make your teeth pearly white in 30 minutes. it costs about $500-$700 bucks though. my sister did this and i was stunned.
another alternative is Zoom, which is similar to BrightSmile, but it's a home treatment. you have to make a mold with the kit, then send it in, and they send the goods back to you, and you wear the mouthpiece for about an hour a day for 7 days. this costs $200-$300 bucks. a friend of mine did this, and had great results.