maybe this helps on the subject:www.vimeo.com/richarddewilde/explosion1
The goal is to enjoy playing and not to work hard to get fast notes or riffs out of your instrument.
It shouldn't matter what you play, as long as you can do it naturally without any effort you are making music.
That is because you have the relaxation to give your soul and hart besides just hitting the right notes at the right time.
Some people feel a kind of speed barrier while playing.
If a guitar player keeps practicing beyond this barrier, he doesn't 'invest' in technique and you will see it gets sloppy and it will result in hard working instead of enjoyment while playing fast. Playing slowly and extremely fast should go with the same ease. Practice slowly to programming in your technique is my recommendation.
Stay at your barrier, don't go beyond, practice untill you can do that easily before you go further. Practice should be fun..good luck!
Richard de Wilde