The biggest challenge with the resin plastic is indeed the cleanup. When I was building my Marauders and Plague, I did quite a bit of converting as well. Chopping that stuff up and modifying the pieces to get more variance takes a fair amount of patience. I did the same thing with my Corporation troopers that I received in the Project Pandora boxed game.
I think in the end it depends on your perspective. For me:
Pros - I like how resilient the resin plastic is, the cost per model is low, and it holds detail well. When primed and painted it looks good.
Cons - cleanup takes a lot of work. It's HARD and therefore more difficult to customize. You have to use super glue (which doesn't matter to me but bothers some).
I'm actually sad that the new Dreadball figures are single piece because I have to chop them up if I want to modify them. The fact that they're plastic however means that it's easier to do than if they were restic. I'm not sure what the plans (if any) are in terms of material for Deadzone's future models.