It is currently early days for the project and there is [sic] currently no major differences between the original Aircrack-2.41 and Aircrack-ng-0.3. As soon as differences appear they will be highlighted here.
Have a look on their site, there's some HOWTOs on there.
I haven't used this tool since wireless is a bit flaky for me as it is, but I'm assuming the fact this aircrack-ng is so new is the reason there aren't that many guides for it...
edit: not sure if this is against LQ rules either, so I've asked a mod just in case...