If you are using G-bit throughout, that is the best thing you could have done for performance. You will be faster flat. (One less packet (layer3) tear-down and build-up for workstation to server packets.) You could try putting your servers on different switches so the bulk of the traffic doesn't all try to go through the same switch on the way to a server. That's the only suggestion I would make.
I think, however, it would be wise to have vlan design plans ready and make future network configs with those plans in mind. It seems that, in my experience, every time I think that everything is status-quo, some body comes up with a `better idea' and I have to make it happen. I think that it's good to be prepared - for whatever that's worth.
