I use them and like them a lot. However, I haven't tried any other brands yet. I will when the batt dies for good. I got the rechargeable one after trying disposable 1st. I believe the website (21stcenturysmoke.com) calls it something like the quick starter kit or something, but I got mine from a local store. It is supposed to be rechargeable for about 30 times. I've gone beyond that in number of overnight recharges plus I recharge it a couple of times a day, but that's only b/c I don't wait the full 2-3 hrs for it to charge during the day. I go through batt quickly b/c I use it frequently all day, not just on breaks or every couple/few hours like most. I need another batt for this, and as ecig365 wrote, when I purchase my next e-cig kit I will def get one with min. of 2 batts. So, I concur with judecat. Trying it out, and realizing that this is the way I want to go, has given me time to research, review, compare, price, and finally order my chosen starter kit for long-time use.
The carts, locally are 3/$10, which sucks. So I have now figured out how to beat paying that much by re-using the carts with smoke juice.
After getting e-juice locally 1st to figure out how to do it, I ordered some - an asst. of samples - from sweet-vapes.com and highly recommend them. It's easy to re-fill the carts.
You just pop out the white mouth covering and the clear ring behind that with a pushpin or paperclip or whatever tool that works for you (personally, I separate and use the inside metal part of a clothespin b/c it's stronger than a paperclip and not sharp. You don't need sharp.) Then take your liquid and squeeze some juice around the outside edge of the wick. Put it back together. Wait a while for it to absorb - the longer you wait (~24 hrs) the better it works, and wa-la! You're good to go.
There are tons of videos and posts to explain this process in more detail, but it's much easier than I had imagined, so don't obsess and over-think it. I've refilled my carts 2-3 times and still going strong, but I imagine that's going to end soon. They have waaay outlived how long people say they last.
I hope this helps you and other newbies looking to try out something cheap.