The number of editors Transmetropolitan had over the course of its run: 6. The number of skulls on sticks in front of Spider's house, helpfully labeled "These were editors": 6.
Transients are both biologically transient in the sense that their bodies are transitioning from one state to another, but the fact that the stigma against them forces them to the outskirts of society makes them cultural transients as well.
Spider's recovery from the I-pollen is foreshadowed when the Farsight guy mentions that they have altered I-pollen to fight its side-effects. Since this was the second time that Spider was exposed to I-pollen, the second dose might even have cured the effects of the first, unaltered dose.