Boots No7 Line & Define Lip Liner in Nude #20 is somewhat of a cult product because it was created by makeup artist Lisa Eldridge. If I remember correctly, Lisa said she was trying to find the perfect nude liner for herself, and Boots No7 Line & Define #20 was the result. I can definitely see why this lip liner has become so popular: it offers an excellent balance of beige and rose that will flatter many. The quality is also very good: I think my swatch demonstrates how smooth it is and easy to use.
My coloring is different than Lisa's, so what I consider as "nude" is a bit different (deep rose, actually). I use Boots No7 Nude as a base when I need to warm up or tone down a color. The finish of this pencil is matte and a little dry (for me). So a lip balm and a gloss/moisturizing lipstick are essential when I wear it.
Bottom Line: nice.
Boots No7 Nude (20) Line & Define Lip Liner ($6.99) is available at Target and from drugstore.com.