I've tried them before. The wicking is kinda critical. You want to make sure you get the entire coil covered, one side of it I mean, don't smother it... I prefer the wick on the inside and air holes facing directly into the top of the coil... As for the wick, it's easy to stuff too tight because you're typically jamming it between the coil and the posts. Kinda like any wick I guess... Not too much or too little... Need to keep the coil wet and too little exposes parts of the coil and let's it get too hot while too much will compress it and keep it from wicking as fast as it should.
As for being impressed.... They worked decently, but wasn't anything to go nuts over.