-Ink not coming out for the few centimetres of writing.
-Ink not coming out if I leave the pen for a few days without using.
-Having to refill if left unused for even longer.
-Leaky tips, dirtying the hand.
-Tips easily broken in a drop.
Somehow I always don't get the instant ink, no matter what pen or ink I use. This is the number one reason I kept giving up.