I bought it the other week and used it for the first time last weekend.
You can use any nail varnish with it (well you have to, it doesn't come with any!) and it's the top coat that you use under the UV light.
It's not a quick process - you have to wait 30 mins for your polish to dry - but it's bloody brilliant. My manicure has lasted a week with a bit of wear at the fingertips. I did it quite haphazardly though as my first attempt and I am very very hard on my nails so I am really pleased with it. I love the fact that I can use all my current nail polishes so am not limited to a particular brand or colours. You just need to follow the instructions to the letter and it's great!