I agree with the others - proper phrase matching is very important. I've heard some mixes where people are "phrase matching" at 4 bar intervals (16 beats). Sounds terrible to the trained ear. Even phrase matching at 8 bar intervals isn't the best. What I have found is that you should be phrase matching in 16 bar intervals (64 beats) for best results. Of course every track is different, so take that with a grain of salt.
Creative mixing is where it is at. Blending in and out during intros and outros, heck just a basic blend in other parts of the track, is about the most boring mixing you can do. It is fine if you are just starting out and learning to beatmatch and phrase match properly. But once you have these down to really take the mixing to the next level you have to start getting creative. I'm talking cuts, pumps, mixing through breakdowns while cutting and pumping, etc. The key to being able to do this (in addition to your phrasing and beatmatching being spot on) is having your levels adjusted correctly. This will allow your cuts, when done in rhythm, in time and in count, to sound smooth and natural.
Personally, I'm a big fan of two deck creative mixing. Someone that is really working two decks to get the absolute most out of them as possible impresses me a lot more than pretty much anything. It displays a true mastery of the technical skills of DJing, a full understanding and mastery of the concepts behind mixing and music structure, and allows for a confidence behind the decks in your moves that really comes out and can take the performance to another level.
Playing with confidence is another key. When you've really mastered the above techniques and are playing will supreme confidence and are mixing with concise and sharp movements, you establish a groove for yourself and for people watching and listening that is infectious. When mixing like this and you hit that double drop after a series of sharp cuts, pumps, etc., you'll even find yourself fist pumping to your own mix.