Picture computer generated music. It's exactly on the beat. And it's sterile sounding, for that very reason.
Ranjay: I agree. Listen to Bob Moore's bass work on Patsy Clines "Heartaches" that I mentioned in an earlier comment. He is right on the beat but he sure as heck does not sound sterile even he he walks it. Also check out "Walking After Midnight". Bob's bass line defines that song. He is bang on the money as far as timing goes but he plays it with great feel and just the right amount of sustain on his notes. Sustain is easier on the upright than the slab though. I really notice it when I play my P bass after the upright so I know I have to work a bit harder with my left hand to control the note length better.
The danger when concentrating on being on top of the beat, is that you end up making everything sound like a march. But being on top of the beat doesn't mean you can't make it swing or add whatever other feel it needs. It's all about the left hand. I see my job in the two bands I play in, as being there with the timing and complement the singers and other band members in what they do. As Bob Moore told me one time "sometimes it's better to just play the one and get the hell out of the way". The "one" is where the timing is.