I've downloaded 0.8.1 RC, Payment module 0.3 with SS 2.4.4
Added the README config to _config.php, although most of it remains commented.
Added to following to _config.php
'DPSPayment' => 'Credit card (DPS)'
Added items to cart, went to checkout, entered CC details, submit and get this error:
Access to undeclared static property: DPSPayment::$cvn_mode in [...]/payment/code/DPSPayment/DPSPayment.php on line 109
Note, the same problem is shown on the Payment module forum at http://silverstripe.org/payments-and-payment-gateway-apis/show/14901. But whether it's a payment module problem or ecommerce use of the payment module I don't know, so posting it here as well.
I have to say, all the discussion about revamping payment and ecommerce modules is great, but some decent documentation would go a very long way to making the effort successful. I don't mind adding/editing documentation as I learn these modules, but where does it go?
Also created ticket in Google project.