it is addicting if you do you it too much (like any drug really)
the way i do it is full up a balloon using 2 cannisters
breathe out untill i cant breathe out anymore then breathe the shit in as much as i can then exhale back into the balloon the keep repeating untill theres nothing left in the balloon then i crack a few more as quick as possible

i stopped tho
i once passed out for 5 mins and well it freaked me out

its a totally different buzz tho sometimes i felt like i was falling sometimes flying
if your gonna take it do it sitting down cos you will collapse to the ground and not be able to stop it