Playing as a renegade is fun. My Shepard is threatening people into giving him discounts, shoving people, and getting into people's faces.  The only time I felt guilty was during Zaeed's loyalty mission; you heard the people screaming as you rush to kill the guy.  Harsh.  Kasumi's cool; she can fight.  We did a lot of damage just the two of us, and she's works well with Miranda.  
 
I'm still not sure about the hovercraft.  It's better than the Mako, but I'm not sure by how much.