(Dis)advantage actually works quite well, since it quite significantly shifts the odds towards the side of the advantage. You'll be fairly confident in doing a roll with advantage (unless the target number is fucking high), and you'll be fairly reluctant to roll with disadvantage. As a bonus, with advantage, you have a greater chance of a nat 20 and lower chance of nat 1, and hey, who doesn't like more crits? :v (also the cantrips are delicious, just saying)
In all honesty though, as iconic as the d20 is for tabletop roleplaying, i'm actually not that big a fan of it in action. It's satisfying to roll, and nailing a 20 is always awesome, but i don't like the flat distribution of results; a seasoned veteran has as high a risk of a natural 1 as a complete rookie. That's also partly why i like the advantage system, since it messes with the otherwise flat probability curve. In a group i once played in (Cypher system, also d20-based), we actually ended up switching to 2d10 instead, which i found more enjoyable even though there were fewer exceptional results. It did make their appearance all the more exciting, however. :v
I thinkkkkkkkkkkk the "pool of d6's" system that Shadowrun uses is my favourite so far. If you're unfamiliar with it, here's the short version: Roll all your d6's for that skill test, count 5's and 6's as hits. If your hits meet a certain threshold (sometimes dictated by an opposed roll), you succeed. If more than half your dice are 1's, it's a glitch. If you get a glitch with no successes, it's a critical glitch. Modifiers are generally handled as dicepool bonuses or penalties. What i like about this is that your risk of glitches scales with your dicepool, so that a rookie is MUCH more likely to fuck up than a veteran, and i like this because IT MAKES SENSE.