Radiogenic was nerfed hard quite recently - it was 6 times as fast as regeneration mutation and required only a tiny amount of radiation to work.
No you want to keep the radiation moderately low - when it starts dropping your stats, it is beginning to get dangerous.
For some actual numbers:
[spoiler=exact mechanic]Radiogenic has a (radiation/100)% chance of triggering once per 30 minutes. Any more than 100 radiation will not help.
When it triggers, you heal all body for 1 and lose 5 radiation.
Radiation hurts you at 150 radiation. When it starts hurting, radiogenic will only slow down the damage and won’t outheal it.
To approximate your radiation level: it drops your strength at 80, perception at 100 and intelligence at 120.
[/spoiler]
This is no longer the case. Now minor radioactivity will make you vomit once in a while and will sometimes slightly drop your strength, while moderate radioactivity will mean you won’t be able to sit in one spot for long, at least not without taking iodine or wearing hazmat.