Ubuntu-Desktop is a meta package. It does nothing by itself. Meta packages exist as containers depending on a number of other packages, which belong to a standard installation. You can safely remove
ubuntu-desktop. Nothing bad will happen.
However, if you upgrade to a later version of Ubuntu, the meta packages reflect the new list of standard applications. If Canonical should ever decided to drop software-center and include AptDeluxe instead, the meta package takes care of that during the upgrade. Worst thing that can happen, is that an upgrade takes manual work, or that some packages will not received (automatic) updates (because conflicts cannot be resolved); the latter may be a security issue.
I'd recommend to keep those meta packages installed, which provide a set of applications that you would typically want. If software-center is the only package from
ubuntu-desktop that you don't need, I'd keep
ubuntu-desktop because Software Center causes no harm (to my knowledge). However, if there's more bloat that you want to get rid of and you don't mind the possible, future issues, removing
ubuntu-desktop is the right thing to do.