We used Dewalts for the 1st time last year. We were extremely happy with them, and didn't really have any major problems with them. We did find that the press fit gear on the CIM output shaft actually moved on us (slid inward) and we lost one of the gears due to this.
(The press fit gear is a cluster, and the larger teeth failed to mesh with the lock-out ring for 3rd gear.)
Other than that, they shift quite smoothly and were relatively cheap. However, I think we'll go back to the kit tranny for this year. It took almost 3 weeks to get the parts machined, assembled, and tweaked. That's far too long to wait for a drivetrain. We're also looking at some similar two speed drill gearboxes. No details as of yet, but we found that the 3rd gear wasn't all that useful on the Dewalt, even with full runs across the field.
Here is are a link to our '06 pictures. I think weeks 3 and 4 of the build pages show most of what you're looking for. You'll also see the custom mounts we made, which was required to run one length of continuous chain.
GUS '06 Photo Album
I can snap some more pictures of the gearboxes if required. Best of luck!
BEN