I first saw the Dynamics connector at Convergence of last year. I was at that time not very impressed and it seems still a lot of work had to be done for making it a solid solution.
I am currently working on new assignment and due to the requirement we have to implement Biztalk 2010 for integration purposes. So I am currently focusing on the heavy weight for integration.
Nevertheless, I also had to look to two integration based on the Dynamics connector and as you might expect they both failed. It was integration between CRM and ERP (Nav and AX). Most complaints I heard that its almost impossible to debug, I also experienced it myself. The error messages are so general that you keep searching untill.... The other complaint I heard that Microsoft support on the connector is bare minimum and seems not to get a lot of attention.
In both cases the solution tends to be to turn to non-free integration solution either of Scribe or even custom .NET solutions.
Of course, I am curious if this was just my bad luck or that more of you have bad experience with the free connector? I also read some post that people got it working, but it didn't say if it was just basic or more complex integration.
Keep it integrated! :)