I understand your position, but I kindly ask you to please keep up with the betas. The core API should be very stable, but there is a difference between beta-2 and beta-3 as you've spotted. However, the Maven team is very responsive so you should not have any problems getting help (as you've noticed by Olivier's comment).
Also, keeping up with the betas makes it possible to spot issues that can be fixed to ensure that Maven 3 will be the best version ever. Not doing this until a RC would delay the release of 3.0-final should you encounter a bug (or a 3.0-final version that doesn't work with the sonar plugin).