Nami is my favorite champ right now. She is rarely if ever banned – I really don't think I have ever seen her banned actually; she can handle things pretty well as a support in bot lane; and people don't usually have a problem if you ask for support in solo queue. I actually feel that I make my ADCs play better as Nami. It's really fun right now as I am slowly climbing the ranks with her as my main.
Her ult is great. Tidal wave can be used for initiation or for disengagement, and can often catch everyone on the opposing team. It can really change a team fight, and can give a Yasuo a huge game.
My favorite ability though is Ebb and Flow. This gives you healing when cast on friends and causes damage when targeted on an enemy. And it bounces between friends and enemies up to 3 times. I'm think I am starting to get the hang of this spell and getting at least 2 bounces most of the time. If I go in front of my ADC, I can zone the enemy and usually hit them with Ebb and Flow and and it heals any damage I take getting in range. It's pretty cool to damage the enemy and almost immediately have any lost hit points restored. If I decide I want to hang back behind my ADC, Ebb and Flow has a very good range since I can hit my ADC with a heal that then jumps to cause damage to the enemy – pretty cool.
With Nami as my current main, I am hoping to gain a few ranks and maybe even get up to silver, but we'll see. I'm not even sure when the season is over.