You may want to look at the
eGo/Tornado. I plan to pick me up an eGo later today when they restock. It's
smaller than the Silver Bullet and has
longer batter life. It only does 3.7V, but 3.7V is what most do and most people think its perfect. Do you want the Silver Bullet because it lets you do 6V? If so, then you may want to look at Low Resistance (LR) atties on an eGo. They are supposed to make your eGo or any
mod with a 3.7v battery of ~420 mah+ work like a 5-6V battery! All without degrading your battery life or risking the dangers of high voltages.
Another thing I've come to learn from reading posts on this forum is that Janty provides the best customer service around. Their products come with long warranties and they are quick to answer your questions when you need assistance. The head designer posts right here on ECF all the time. Check out the JantyWorld subsection.
I don't own an eGo or a Silver Bullet myself. This information comes from all the research I've been doing the past few days. Hope this helps.