Hello and Welcome to Windows7forums..
I'm assuming you did an Upgrade and not a Clean Install? (Not recommended but if all is working fine then no worries..)
In answer to your question that all depends on what you want.. No matter which version (upgrade or full) you buy you'll still have to do a clean install as you can't just upgrade from the RC to the Retail..
Unfortunately..
However, if you buy the Upgrade Media you can still perform a clean install with it.. The only thing is with the Upgrade Media you have to install twice in order to be able to perform a clean install and activate Win 7.. (It's a little workaround that many don't know about).. My advice is to NEVER pay full price for an OS..
If you buy the Full version than obviously you'll be able to just do a clean install and activate all in one session.. So, yes the full version means less work but also means you'll be spending $100 more then you have to..
Sorry if I made that a bit more confusing then it needs to be..
To summarize, you can do the same thing with the Upgrade Media that you can with the Full version (it just takes 2 installs with the upgrade media) and No you can't just upgrade from the RC to the Final Retail version..