I wasn't around for the Three or Five Doctors but I'm told they were very exciting by people who were young fans at the time. Doctor Who repeats have always been thin on the ground, clutches coming along with the Five Faces of Doctor Who in 1981 and the stories chosen for repeats on the 30th anniversary. Other repeats have been scattered across a the last decades, a Power of the Daleks here, a Genesis of the Daleks there. The last repeat of old Who I can recall is Hand of Fear on BBC 4 when Elizabeth Sladen died. Point being that when the Three Doctors came along, Hartnell had been out of the part for 6 years, Troughton 3 years, and neither had ever been seen in colour, only still pictures in a tiny handful of Doctor Who material. I still have my father's 10th anniversary Radio Times, in which were episode listings which probably made it the first programme guide published for the series. This made the Three Doctors very special, and some who were young at the time recall it being extremely exciting.
There is a big difference though between the viewer experience then and now, created by the home video age and the rise of digital channels. Note that from the Hand of Fear repeat, old Who is now deemed BBC 4 material, to be shown alongside documentaries on Stradivarius violins, not BBC 2 as when the 30th anniversary was on, and certainly not BBC 3 where new Who is seemingly on constant repeat alongside Family Guy and programmes about yoof culture. Still, between DVDs being sold cheap in HMV and regular repeats, new Who doesn't suffer the problem of old fans in the 70s. Any time they want to see Eccleston or Tennant they can flick through the channels, go on iPlayer or get out their DVDs.
But although that takes a lot of the edge off seeing previous Doctors on the screen again, the fact that people still watch these repeats shows there's continued interest in them. Furthermore, children are now growing up watching Doctor Who with no memory of the Eccleston era. They are as much part of the past to a 10 year old now, as McCoy was to me when Paul McGann made his only appearance as Doctor Who. To produce a new story allowing both young fans to see Eccleston in action for the first time, and for slightly older fans to see something other than reminiscences on DVD, would be grand. It wouldn't matter if the plot was contrived because people want to see the characters in character. It would be hugely entertaining. The worst thing they could do is try to make a clever not-traditional multi doctor story in order to get the actors in but not have them play the roles we love them for, something pretentious and confused like Zagreus, for example.
No, Five Doctors good, Zagreus bad. Stop trying to be clever and have fun.
As for the rest of the anniversary? Well as I'll cover them another time, but they range from some great DVD releases, such as the Mind of Evil in full colour, a set of reprints of old novels with some dubious choices, and rumours of supposed missing episode discoveries that are being held back from public knowledge. But reading around, these rumours span the view that there's nothing at all, to those claiming that a 'major haul' has been found. I wouldn't put too much hope in that one.