I played it to completion. Then Rebirth came out and I played it to completion (barring The Lost, because come on). I only recently picked up Repentance and I'm already another 200 hours in.
Yeah it was only pre-holy mantle that I gave up on, The Lost is actually a pretty interesting character to play now. Is Tainted Lost still slightly easier than original Lost though?
Think the original Lost but nearly all defensive items are removed from the item pool. On one hand that means no useless health ups clogging the item pools. On the other hand, that means no holy mantle or dead cat.
Overall I'd say that makes him a more consistent and more fun character, but I'm not sure if I'd call him easier. Losing the ability to find things like dead cat hurts.
IIRC (been almost a year since I've played Isaac), he has a higher damage stat as well, which is great.