It's not so much the speed (per se) as the speed at which things appear to happen. I rarely have time to look at the ASI - usually a quick couple of glances as I turn in from downwind (180 degrees continuous turn) and get established on the right descent path, then one more on short (very short) finals. The 2500' sink rate, coupled with the speed and the poor forward visibility, mean that everything seems to happen fairly quickly. And the short-coupled fuselage and bungee main gear mean that if your speed is a little fast, or the flare a little high, there's a good prospect of a bounce.
Like all aircraft, a good landing starts with a good approach, which starts with a good circuit, and a 1000' circuit in my S-2C takes around 2:20 mins, which means that you're constantly getting baulked by Cessna 150s flying 5 mile downwind legs.
None of the above puts the Pitts beyond the reach of an average pilot, as much as we Pitts pilots like to pretend otherwise. You just need a good instructor and plenty of practice to get used to the picture and get the brain used to processing things at the right speed. In that sense, it's a bit like the first few hours of PPL ab initio training, all over again. But it's great fun and provides a challenge that never really goes away.