I will work on a video on this topic eventually, but for now, I just want to mention how extremely important it is to practice timing.
Many of my students can play pentatonic licks and blues rhythm patterns. Problem is, they often struggle to play it in time.
Simply put, playing with good time is a necessity for anyone who wants to sound good.
So what does good time mean? It means that every note played is accurately and tastefully with respect to the tempo. For more info on tempo, see http://en.wikipedia.org/wiki/Tempo and http://en.wikipedia.org/wiki/Meter_(music)
What I'm getting at here is how to improve timing. Use a metronome, drum machine or groove to practice playing 1/4 notes, 1/8 notes, triplets, etc; at different tempos. I think good backing tracks are great for practicing. I mean, playing to a metronome, how fun is that? Having a good groove going makes it so much more fun to practice.
A great way to improve is to record yourself practicing these things. When you listen back, you might find yourself thinking, wow, am I that off really? I have had that realization quite a few times myself...
I have throughout my years of playing spent a lot of time with drum machines, and I learned a lot from it. It is time very well spent to work on rhythm, timing and meter. It is one major and very apparent difference between a great guitar player and a mediocre player. Take any good players like for example, Robben Ford, Keith Richards, SRV, Yngwie Malmsteen, Johnny Winter or David Gilmour - they all play with great time (I intentionally mentioned different type of players). They of course have other skills too, such as good technique, tone, and experience, but without good timing, they would sound like basement wannabies.
I started out by practicing scales and technique when I was young, and I got pretty good at it. Problem was, when I joined my first band, I sounded so terrible I couldn't believe. The problem? My timing was off the wall! I remember well an audition I did, and I did not get the job, most likely because I could not play tight. I went home and practiced with a drum machine and starting thinking about music instead of guitar, and my playing improved immensely.
So, I strongly recommend working on timing and rhythm early on, in order to become a solid guitar player. It is one of those things that people expect, and if timing isn't good, it becomes VERY apparent.