Bought Nami, after getting a game where someone not playing Nami called support and lock after I had her selected (and like 4 dodges), I finally got her. It was a blast and I was hitting Qs all day, but it made me realize exactly why I don't play support. -_- Failures! Failures everywhere!
But yes, she is hella fun. Her ult is fantastic though I'm still getting used to it's use. Not quite as close to a Sona ult as I previously thought.
The Q though. That Q! Once I got used to it's range I was hitting them all day. Took a few tosses to get used to the speed of the bubble, but once I did I was able to hit chasers and runners as easily as stationary targets.
Here is my biggest issue though. While she is easy and fun to play, she requires more coordination than most. On Leona, ADC sees the shield go up and they know you are about to dive in. Blitz grab is self explanatory. With Nami it isn't as obvious, so you really need that extra communication to make the best out of her.