It comes down to what you know, and like to use. Sure, there may be "better" gateways in your opinion, but when I've already invested hundreds of hours developing on the most widely known gateway, I think that no matter what, it would not be worth retooling my entire portfolio to go someplace else. I'll always recommend Authorize.net to clients specifically because of that. I've had clients that opted for the "cheaper" alternative, but in the end, they have to spend more on development time. The return on their investment, to save a few pennies per transaction, can reach 5 or more years. The point is, we're here because we use Authorize.net and because we want to make it a useful tool for our clients... not because we want to hear your unsupported claims of greener grass.
Why don't you suggest ways Authorize.net can improve their support, API's, options and rates instead of just coming here to complain?