the only thing i would add is that once you have your american express merchant account, login to their website and immediately switch to electronic statements. otherwise they charge you a $5 fee every month for paper statements.
So your article might have been better titled "6 things they don't tell you about authorize.net"...
That should never happen.
If you have full AVS checking, you might hit against the incapability of most users (quite understandably) to type in their address exactly the same way as on their credit card bill. For this reason, we (at my previous start-up) disregarded the address part of the verification (but still required post code and CCV2). Address failures aren't a good indication of fraud, since most legit users will mistype their address.
We'll look into what AVS options we have available, and I'm also reading through the Protx link you posted.
1. The web sites for credit card processors & merchant account services are completely useless
That depends on the site. Protx has awesome documentation at http://techsupport.protx.com/ (see the "Advice" bit on the left). I'd even use it when building for other providers, because much of it is very generic.
3. Address verification (AVS) is voodoo
All the verification systems are voodoo (except the security number). Hell, even the credit card number is voodoo. Why? Because the customer could have made a mistake while typing them in. The bank lets you decide how to handle it. That is a little unclear to most cc processing beginners, but it can be resolved easily: use 3D-secure. This shifts the liability back onto the bank and you don't have to worry about that crap anymore.
4. Test charges are pretty much unavoidable
Both of the times I've had to build a cc processing system, I haven't needed "test charges". If you really need to verify a card ahead of time, don't use test charges, charge a proper setup fee. Why do you think so many sites charge setup fees?
6. Errors are incomprehensible and your credit card processor is useless at helping you solve validation issues.
Dunno what kind of merchant they're using... I get descriptive errors from my accounts.
7. When you ask why stuff doesn’t work, even due to Stuff Nobody Told You, they think you’re kinda dumb.
Again, it goes back to the first point... get a better provider that has decent documentation.
Credit card processing is a pain, but it's not that terribly hard.