speed is somewhat important, but i personally hate it when a guitarist is playing a solo and just shreds all over the fretboard. to me that shows the player cant think of anything and has no songwriting abilities at all. playing a solo in a song should be melodic, something you can hum. playing a solo by yourself is more appriate to shred. but it IS important to learn to play as fast as possible, so you are not limited at all!!:)