They all have a nice face when they start off; once their business is down, they start showing their dirty faces and lack of ethics.
I had had bitter experiences with howtodothings. com and bukisa.com. Payments were from Google Adsense directly in both, but the sites played dirty with my content. Howtodothings closed; bukisa is still there, sitting pretty with my articles with no response from owners for my requests to delete my articles.
Helium was nice, but they started gradually becoming uglier and uglier. But I did not have payment issues. The site is closed.
suite101.com also got closed, but fortunately I didn't have payment issues.
HP is virtually the only site that keeps fighting valiantly and trying to remain floating, when most of the competitors have sunk; they have not bartered their business ethics so far.