I much prefer musicians who may not be at the top of their class but can throw all their emotions into the song. Like some metal guitarist who prides him self on being able to sweep perfectly and play 25 different notes a second in perfect time, and a guitarist who doesnt know what sweeping is but can play a 5 note solo that makes your hair stand on end. Thats why I love blues, not the most challanging but one of the most emotive.
Because I can't resist taking the bait...
While this is, to an extent, true, there are also guys who can have it both ways. I'm a huge Satriani fan, and at his best he can play 25 perfectly executed, perfectly controlled notes a second, and STILL make your hair stand on end.
I cut my teeth playing blues and grunge rock before I got pretty heavily into shred-y stuff, so I definitely appreciate the slower, bluesier stuff too, but a lot of guy automatically hear speed (or, even worse, hear that a particular player HAS speed) and stop listening, lamenting all these emotionless chop-fests. Sure, maybe 8 times out of ten that's true, but a lot of the truly great players with technical aptitude - Satriani, Timmons, Zaza, even Vai and Petrucci when the former isn't being weird and the later isn't showing off - are great precisely
because they can bring emotion to bear on technique and make it serve the song.
Anyway, to at least pretend like I'm on topic here... Even when I'm demoing with just drum loops, I rarely have fewer than 20 tracks and play. Sure, not all of them are "fundamental" tracks - I'll double rhythm guitars or, if acoustic, often record in stereo to separate tracks, I usually record melody lines and solos to different tracks and then bus them, and I can't resist overdubbing ebow lines or random guitar noise here and there - but if you're doing even a simple rock mix things add up pretty quickly. Making it work is just a question of not letting anything get too big and dominate anything else.