Hi David,

I've never did a migration from CC to RTC, but some migrations to CC or CC UCM, so I have some experiences.

The main points missing from my point of view:

Configuration management process:
Can you rebuild all the structures used in CC in RTC?
Can you rebuild all the functionality used for your SCM process?
I have seen several posts in this forum, saying "We have moved from CC to RTC and we are missing following feature(s)..."
Example: Based on the "missing" pessimistic locking regarding files, you may run into trouble, if several users change a non-merge-able  file simultaniously.
If you are using CC UCM with lots of rootless components, there might be a problem to use such structures in RTC.
What about reports, metrics...

build/make process:
All the homegrown scripts/tools has to be checked and modified to be used with RTC.
Functionality like build-avoidance or build-auditing, delivered with CC, are not part of RTC afaik.
If you are using those functionality like shared derived objects or configuration records, you have to look, how it can be implemented with 3rd party tools.

integrations:
- diff/merge tools (shall be available with 5.0)
- Explorer/TotalCommander...
- IDEs/editors
- process integrations with CQ or other tools
- triggers

training:
If you are using CC UCM, the training effort may not be a problem, because the concepts with streams, components are similar, even if the names in RTC might be confusing.
If you are using CC with an extensive homegrown branch structure supported by homegrown tools, it will be more work to be done in the trainings.

Hope this will help.
greetings georg. ;-)