I will only miss those few users that I often chat on here, but we have talked outside of gag as well, so won't really be missing much. But yeah, when some users that I talk to often, go on hiatus and I didn't know, I'd be curious and will have the feeling of asking them.
It has only been a day, but I already miss @linkwinky. I miss @Rcjh1987, but she is only on break and will be back. there are others, too, but those are the two I notice being not on here the most fight now.
I think users build up a close network of friends over time and if they left those within the closest of circle of friends would miss them on GaG but they probably have their contact details. On wider scale there are 3 who left in last 3 months I miss and if any of about 10/15 of the current users left I would miss them.