I like this trend, but, as with the socks and heels trend, I find that it can be tricky. Anything over the knee, be it socks or boots, can look trashy if not done with a light hand. For my own taste, I find that brown ones look more sophisticated than black, since brown boots have a more rustic look to it, while black ones can hint at a dominatrix vibe when worn above the knee. Also, the heel is key. Flat boots are a sure way to keep from looking trashy, but I also like heeled ones when the heel is a little thicker and not too, too high. Again, rustic rather than dominatrix.