When clicking Latex / Preview Document, TeXlipse starts a command, which may fail, for example because the parameters are incorrect. When it fails to start, the user may think that nothing happened and might not know where to look to diagnose the problem. It took me quite a while to think about looking at the console for the output (I first searched the eclipse error logs).
Obviously TeXlipse can't detect wheter the started program exactly does the right thing, but at least it could detect if the program closes immediately, and display an error message, possibly containing the text output from the viewer.
Also maybe consider sending the error messages (those sent to standard error) from the viewer program to the eclipse error view instead of (or supplementary to?) console view? (Admittedly this is debatable and perhaps depends on the verbosity of these programs error logging.)