Imp is probably over powered, but it's a beta, that's the kind of thing they should be looking at. My biggest complaint would be that I haven't found a plant variant that I'm as effective with as I am with the computer scientist. And it might be largely due to the imp being over powered actually. Pretty decent with the orange guy. I also don't really like the goat thing.
Overall though, they took the first game, added a bunch of shit and cool features, I'll buy it. Really stoked that my characters from garden warfare 1 will transfer.