What are you cutting in FCE? If you are satisfied with what you have stick with it. There is no need to upgrade if you don't have to. FCP X is quite different from FCE.
In any case, there is a fully functional trial version that you can evaluate for 30 days. And you should be able to run both on the same machine.
"I'm pretty satisfied with what that program can do, but with FCPX having come out, I wonder if it may be worth the $299 you pay for it. "
Worth $299? Absolutely.
New learning curve required. X is a whole new game from FCE/Pro.
Many of the features of Studio are incorporated into X so $299 is a steal in my opinion.