I personally have not used AWBS (http://www.awbs.com/) but I know other people who have and say they really like it. Like many things alot depends on the person using it and their preferences.
I have looked into it when I first started with the company and then again last year, but I figured it does not have 1/2 the features I'm used to at WHMCS. It also does not offer a lot of choice when it comes to payment providers and registrars. Overall I thought it was to expansive for what it offers.