The Blu is a well thought-out "everything you need in one package" product. It is perfect for sneak-vaping in airplane lavatories. (Not that I recommend such things, of course.)
Positives -- it comes with a nice PCC that works well and has everything you need right out of the box.
Negatives -- non-standard battery (its polarity is reverse the standard 510), limited choice of flavors, really bad battery life, no manual battery option.
The Blu was my introduction to vaping -- I got one for a trip I was taking where I'd have a long airport layover. It worked fine for that.
But as an everyday vaping device? IMHO both the standard kr808d-1 and 510 systems run circles around it.