"No Intellisense with VS 2010 RC (and how to fix it)" is a blog post by Scott Gutherie about a couple of things that are different between RC and RTM. "Visual Studio 2010 Released" by Scott Hanselmann has a reference to a change between RC and RTM as well.
To be more specific in each:
First one references a blog post noting:
Why were the default options for
Intellisense turned off when I did a
fresh install of Visual Studio 2010
RC1?
The second one wasn't the right link, so I did change it, here's the key quote:
A little confusion about this in the
comments. Folks feel very strongly
about this stuff, understandably. Just
like color blindness, some people are
sensitive to this stuff and others
"can't see it." One person in the
blogs didn't like go for
"indiscernible" and showed a
screenshot. Here's the deal. If you
are running VS2010 RC, you don't have
this fix. This will be in the RTM.
Here's a 100% screenshot, followed by
the zoomed in version. The takeaway is
this. If you didn't like the rendering
before, you will now. This is/was some
subtle stuff, but it's indiscernible
in the RTM, so be happy! I took the
screenshot from a daily build, not the
actual RTM, which hasn't happened yet.
These aren't the only changes probably, but these were references to what I could easily find about it so I'm trying to give a useful answer here.