I've owned an ARES WA2000, which apart from the bolt-action implementation, was a great quality rifle. Didn't have any problems with it while I had it.
I currently own an ARES SL8, which has decent build quality but QC could use a little more work (my front handguard is all wobbly and creaky). Can't comment on the internals yet. I guess I'll find out over time.
One thing I will rant about is whatever happened in the HK factories that screwed up production of the ARES SL9. I had one on preorder for months before I cancelled it and went with the SL8. Something about a broken mold or big production problem. When asked for an estimate, all retailers say 'next couple of months'