The frustrating thing about Shada is that, at the beginning, you almost think that more footage has been shot than you've heard about. Almost the entire first half of Episode One plays out as it would have had the story been completed, thanks to most of the scenes being shot on location on film, and thus done first, as per normal production standards at the time.
We're also spared a great deal of the whimsy that would have probably found its way into the script, although with Douglas Adams editing his own material, this might not have been the case. There still is enough humour to carry the day, though, particularly in the first Doctor/Romana scene that sees The Doctor's attempts at punting on the Cam go tremendously wrong.
The centrepiece of Episode Two is a chase through the streets of Cambridge as The Doctor, on a bicycle, tries to escape the mysterious brain stealing sphere of Skagra's design. It's a well shot sequence, and I can't help but think that somehow this sequence would have made for a much better insertion into The Five Doctors than the punting scene that was eventually used. Instead of the sphere, The Doctor could have just as easily been running away from a black triangle, couldn't he have?