Otan :me and my wife are expecting - something like six weeks from now....

Vibrato and bends top my list of what can make a solo work or fall on it's face. I could listen to Freddie King play the same 5 notes endlessly because he makes the guitar sing. Rhythm is also very important when laying down a solo, you gotta play off the beat and I hear to many folks that don't connect those dots. Solo's don't need to be virtuoso to be compelling, IMO most aren't. I think the blues are a great thing to really delve into, I play lots of scales but the pentatonic is always my starting point.