There are advances in the 2010 version over the 2007, but many people will not notice them. The changes are subtle, such as the ability to edit the ribbon.
The major reason for seriously considering the 2010 version is that of support - both versions are currently fully supported by Microsoft but this will not be true at some point in the future
A the cost premium is not great, the fact that Microsoft support for the 2010 suite will continue for several more years than that for 2007, would be a good enough reason to go for the 2010.
One thing to check is if you use any particular add-ons - confirm that these will work with 2010 before purchase - should not be an issue but important to check none the less.
There is also the trial option of Office 2010 - this would allow you to make up your own mind as to how it works with the way you do