Linux-Based Thin X-Terminals?

Yet Another Anonymous Coward asks: "How easy is it to set up Linux boxes as thin clients? My boss wants to use some old 486 boxes as X terminals, networked to a largish server where all applications are run. Has anyone tried this? What is the minimum software that needs to be installed on the X terminal systems? My boss likes open source software because it saves money; Is this another way he can save money?" Obviously the use of older machines is going to ease the costs of putting PCs on employee's desks, but are there other advantages (or disadvantages) to a setup like this?