The desk I'm typing this on is a 2x4' sheet of birch plywood screwed to a TV cart (it's the perfect height for my Steelcase chair). The edges are just as unfinished as that particle board, but haven't caused me any problems in 4 years of use.
Are you planning on keeping this setup, or migrating over to something else?
The 4' width seems to be the biggest drawback with shelf-to-desk conversions like this. Dual monitor setups featuring screen sizes beyond 24" commonly require more than 4' width.
