The KR808D-1 is the best ecig I have found so far. I like the two piece design with a disposable atomizer in each cartridge.

I liked the M401 when it worked, but, being a heavy user, I could never count on it working really well for more than an hour at the most.

Like the M401, the 510 was good when it worked, but the cartridges and batteries had even shorter lives than the M401.