I'm not capable of telling you good/bad match ups. But mechanically, I like her a lot. She can peel, harass, sustain, disengage, and has a movement speed and damage steroid. In general, though, enemies with a dash ability are tough to land bubbles on. The thing about Nami's bubble is that it takes the same amount of time to land wether you place it right next to yourself, or at maximum range. This makes it very easy for anyone with a dash to just avoid it. Her bubble works best on predictable champions. Take draven for example. If he's chasing his axes, you know exactly where he's going to go and can plan accordingly. This forces him to drop his axe, or get hit by a bubble. The positive of dodging far outweigh the consequences of him getting bubbled, so I find that hard to call a favourable matchup for Nami just because he's predictable. Enemies that root themself in place for abilities (like a long range blitz grab) are easier to hit.
Overall team comps? She can set up yasuo ults, she can follow up a malphite ult with a bubble and disable them even longer, and send her ult at them afterward for a triple threat. So those are also things to consider if you're looking past the laning phase.