Hi Blownpony,
Welcome to the boards. It sounds like you are doing the right thing and trying to get advice before you buy anything.
When I first setup my tank about 7 months ago, I bought CC on the recommendation of the LFS, for the same reason that they told you about maintaince. CC is a pain in the butt, I could never keep my nitrates down, which in turn would cause ugly diatom algea blooms, which made the CC look terrible. I changed it out to a DSB about 6-8 weeks into the tank being established, and it was a task I dont think I ever want to undertake again. Changing the substrate in an existing system is not fun, and it adds expense, as well as extra work on your part.
I have been completely happy with my DSB (which cost much less then the CC I got originally) As far as maintainence, there is none. You do not vaccum a DSB, you want to leave the sand bed as undisturbed as possible for it to be effective. Nitrates are not an issue in my tank any longer, they have not risen to a detectable level in months (with normal tank maintainence - I don't want you to think I just put water in and don't do anything - regular r/o d/i water changes are performed)
As far as a mated goby/shrimp pair, the burrow is usually made of loose rubble, not necessarily CC, one tank I looked at recently had a pair with a DSB, and the goby had piled up rocks around the burrow to help protect the shrimp. I don't think the shrimp or the goby could burrow in a CC bed (I may be wrong on this one though)
If you have not already gotten some books on the hobby I would strongly suggest you do, The Conscientious Marine Aquarist is a great book, that has some great advice.