This example is rather contrived, but if you can exert a high degree of control over the creation of meshes it’s possible to get some nice topological smoothing. The base geometry of the second image is composed of all quad faces.
This definition uses WeaverBird 0.2 components (thanks Giulio!) so you’ll have to install the plug-in first.
It’s pretty easy to make this geometry go wacky and if the smoothing level gets cranked up too high you might crash GH so be careful, but break-a-leg.
bridgeSrf.ghx (Right-click on link and “Save link as…”)