My name is Deepa and I work for the Social Media and Community Team at Dell. Flashing the BIOS can correct bugs or compatibility that has been discovered - this will generally increase system stability. In some cases, flashing the BIOS will even give performance increases. Look where they have the new bios. There will be a list of things the new bios fixes. If you need the fixes, flash the bios. Overall, I would say yes most of the time it is important.
What Deepa says is true, but it can also be a very risky process if you choose to flash the bios, if the update doesn't complete properly you might lose access to your system permanently. So, make sure that you have everything protected and backed up before you do so.