I'm currently sorting out a proposal for an in-house web app build, and design is a factor that I'm thinking through. I expect there's minimal budget for design, but I want it to look good, so some tips here might help me organise a good-looking app for cheap!

Now there's lots of advice out there for website design, but less so on how web apps should be designed differently.

One such point where I think the design differs - clean, flat designs are clearly the trend with public-facing websites, however I find that many business web apps tend to throw in a good handful of bold gradients, shadows, and other decoration into the design. E.g. Harvest and Xero.

Is there a good reason for this? At a guess, it might be easier on users who are used to Microsoft Office's outrageous amount of gradients and shadows. Lots of gradients & shadows = it's business time?

But flatness of a design is just one factor. How should the design for a productivity-first in-house web app differ from a normal, public website?