Don't go with the pre-filled cartridges, use juice and fill them yourself. Also, don't just buy any old juice because there is a huge difference between cheapo juice and good quality stuff.
I personally use the Smokeless Image Volt hardware but I would not recommend their juice.
It's goddamn near impossible to find unbiased reviews since everyone's an affiliate but this Reddit sub is a pretty good discussion group:
http://www.reddit.com/r/electronic_cigarette/