What software version are you at?
The latest release for RMS right now is 2.0.0123
I would make sure that you are at that version.(help and about)
Do you have support through a partner? Do you need support?
If you are at a earlier version than 2.0 and paid for the upgrade I would contact my partner and find out were my software is?
The biggest advantage of having support with MS is the product updates. Saying that POS2009 is Q2 of 09(at least that is what some say, Others say early 2010).
The business advantage plan entitles you to 6 Support incidents with Microsoft and free product updates throughout the year of the contract.
What would I do, I know the software well enough I can support myself and would skip the MS support. I would even support that thought even more if I had support through a good partner. But I am not you and it comes down to business need. How comfortable are you with your partner and are they meeting your needs and if you need support well you do.
If you need more input or details dont hesitate to give me a call.