I use Gravity Forums on 4 of my sites and will never use any other form plugin again.

* Simple to use

* Heaps of features to suit my needs.

* Plenty of updates for new features, bug fixes etc

* Great support (Carl even setup a test form showing me how a certain form would look even before purchasing GF).

* No other forms plugin matches GF by a mile!

Been using it since it's release....