Objective: I've used empower and smart and prefer BBsmart. Seems to load images more consistently for me.

Subjective: The nail in the coffin for me was the signature issue with empower that a couple people have mentioned. It's one thing to put that stuff in trial software - where the software is actually sending email through its servers, but after I own the reg code I think it's a little....ummm, disconcerting. My friend was sending me emails from his business addy and didn't realize that empower had preempted his sig.