If you liked Deadlands d20, you'll like Hell on Earth d20. I don't think it's going to bring in many new folks, though.
It uses the same systems (fate chips, spell points, the Harrowed, etc) as Deadlands d20. Most of it is pretty good, but the arcane section needs work.
There's a list of prohibited clerical and druid spells, but no one casts clerical or druid spells. There is a list of prohibited sorceror/doomsayer spells, which I guess also applies to sykers, since they also cast arcane spells (personally, I'd use the lists from the Psionic Handbook for the syker base powers, but I realize they couldn't do that).
The spells are unbalanced - some (brain blast) are so overpowered that everyone will take them - I mean, really, a 0 level spell that does 1d12 + 1/level? Even with the will save and the required attack roll, it's just too much. On the other hand, there's Arson, which is a 3rd level power, which does a flat 2d20 damage (area of effect: a diameter equal to caster level in feet). Off the top of my head, I don't see why anyone would take this instead of fireball.
Still, overall, I like it. It has a nice apocalyptic feel to it that's generic enough that you can do a wide variety of mutant-bikeriding-dirty-apeman campaigns, if you don't want to use HoE's history. Even though there's so much overlap with Deadlands d20, I'm glad I picked up HoE d20.