I have a Hammond, but it's too hard to keep up. Right now it's living in my parent's garage.
The B4's presets are good, but the interface really shines. Tweaking the sliders always makes me smile. The sound responds just like it would on a real organ.
It's impossible to perfectly simulate a Leslie, but this is the best fake I've heard.
The overdrive and mic position features are an unexpected bonus. I even use it as an FX plugin for other softsynths to dirty them up.
This is the synth that got me excited about plugins.