I've been using TheBat! around 2000-2003, back in dial-up days. It wasn't free back then (Opera wasn't either), and isn't free now. It was/is great, but I didn

I've been using TheBat! around 2000-2003, back in dial-up days. It wasn't free back then (Opera wasn't either), and isn't free now. It was/is great, but I didn't find a compelling reason for myself to shell some bucks over their way vs. using Opera Mail or Thunderbird. What are the killer features for you?