I listened to Heartwork the other day. I never really payed much attention to it in the past. I'd heard mixed things about it - but I bought it a few years ago anyway.
Anyhow, after maybe 18 months of not listening to it in full - I almost cried. It's a horribly generic album, with a lack of any sort of song writing cohesion. It has a few moments with some cool riffs and rhythmic patterns, but other than that, it really isn't great. I like Necroticism though - thats a cool album and Jeff Walker's vocals are wicked (inlcuding Heartwork).
But yeah, as far as Heartwork goes, its pretty much just a mediocre album that should probably be forgotten.
Overkill is cool too, but there are better thash bands and it is understandable to not like Bobby Ellsworth's vocals, much like Mustaine, I think hes an acquired taste.