Your thoughts sound a lot like what I found out myself about 6 months ago. FYI, there is a long-running thread here about the SIMS integration with Moodle. Capita have produced more that just web parts - there is also a restricted IMS web service profile, but the Moodle web services stuff that will integrate with it is still in its infancy.
Having had the demo from the RM guy, I have to say that it seemed like a glorified content delivery system, with little to offer in the way of collaboration or communication. Moodle for me all the way
Matt