I never played in a cover group with backing tracks, but did several original shows... and half of them trainwrecked in one way or another. One I remember they insisted on my playing bass over the bass, and it just sounded like a horror show to me. 2 others, we couldn't hear the tracks in the monitors, and I don't have to tell you how the rest went.
I don't have anything against using backing tracks, and actually wish some of the cover groups I play in would use them. I do however think there are some things that people need to be really careful about.
1. Not overdoing it.
2. Not overdoing the bass.
3. Making absolutely certain beforehand that the entire band can hear the tracks, or if not, that the drummer is impeccable, and that he/she can hear them clearly no matter what.
4. That the band is well rehearsed.
5. That the band knows the count on each song before either the tracks, or the entire band kick in.
I'm sure there's more to be careful with, but I'm not completely awake yet

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One of the last original groups I played with, our soundcheck got nixed, and we couldn't hear anything but drums when we hit the stage. Drummer counted off the first song, but either screwed it up, or decided to click in before a 2 count snynthesized intro. It was the bands first performance ever, pretty decent crowd, adrenaline pumping - and, well, it's something I'd really like to erase from my memory banks.