I have 3 glass ones from IBTanked, which I love, love, love!
IBTanked - Get Tanked With Us! I also have a polypropylene from Valley View Vapes, that works great! I only love it slightly less, because it isn't as pretty (VVV has glass
tanks too. I haven't tried them, but they get good
reviews):
Welcome to Valley View Vapes - Your Home for Quality Inexpensive Tanks and Vaping Supplies
Once I started using tanks, I have been in heaven. I don't like to fiddle around with stuff - changing heads, dry burning, etc. Now I can just put a carto in a tank, and except for filling with liquid, I'm good for a least a week.
ETA: I should have said at least a week if I was just using one tank exclusively. Since the 4 tanks have different flavors and I rotate them, I've got a couple that are 2 months old and still have the same carto.