Only problem with TU web disputes is that if you still have an outstanding dispute, you cannot review your file or dispute anything further online until the previous dispute has finished (and updated) on their system. Sometimes the online update takes a week after the dispute is completed.
But otherwise, TU's and EX's online disputes are not bad systems. Although EX has the nasty habit of popping up messages saying - "this dispute cannot be processed online and must be done over the phone or in writing."
As has been mentioned in a previous thread, if you DO do a phone dispute with TU, ask to speak to a US customer service rep, because otherwise you'll be dealing with someone in Mumbai who is only looking for something to tick on his checklist of dispute reasons, not actually understanding what category your dispute should truly fall under.