As mentioned recently in the usergroup forums, the last time we tried to change the way links are displayed it caused an uproar! However one of the main recommendations of my usability report was that visited links should change colour. This is particularly important in the support section so that you know which pages you have already looked at (either so you can avoid looking at them again or so you can find them more easily if they were useful). It is less important in places such as the member centre.
Blue underlined links are certainly the easiest style to recognise but they are not necessary in all situations. As long as link presentation is consistent and links are easily differentiated from text, even on a first visit, then that's fine. Currently, however, neither of those requirements are met.
What are your thoughts on links presentation?