I just had a neat Ick Purist (my first Ick Purist, Ick scares me) run (halfling thief) with early GG - got a soul orb earlyish so could actually get around. Absolution + humility at level 3, desecrated Binlor to get through gold piles and so I could get humility right away (probably unneccessary/a mistake). Got up to 100 piety at around level 6-7, converted out to JJ and instant petition because, y'know, halfling thief. Took Bleaty down at level 7 with fireball + weytwut while using the health regen from mana pots to clean out other mooks and then beat whatsisname Naga at 8.
Would've been unstoppable as well but I lost the top row and didn't realise it.
Anyways, very imperfect run but fun to work with - main thing is, on Ick you can and usually will reliably either poison or mana burn yourself every time (and save a couple of conveniently placed plants for later) before you level up (and there are weak undead, which is very helpful), so GG can really stack up the piety gain there. If I hadn't been using the most potion-dependent race/class combo I can think of I'd probably have stuck with him for enlightenment + cleansing.
Also, changes to the earthmother's clearance boon a patch or two ago - she's a definite no-go on Ick and the druid one now (maybe go in, slow, convert out instantly).