So the Avro Arrow was a supersonic interceptor. First, without actual combat use, it's impossible to assess the Arrow's real-life performance. But looking at the specs and its place in the development of supersonic aircraft, I'd call it cutting-edge, but not terribly far ahead of its time.

It's important to talk a bit about the background of supersonic aircraft. The sound barrier was first broken in the late 1940s. But aerodynamics at those speeds were very poorly understood. What was known from observation was that craft approaching the sound barrier developed somewhat unexpected flight characteristics. We know now that was from the airflow becoming supersonic over parts of the plane, which creates somewhat bizarre effects. Transonic flight is very messy. To give a bit of a 3-second aerodynamic explanation, shock waves through the air, such as sound, travel at the speed of sound, or Mach 1. When an airflow is supersonic, the effects through the air travel in different ways.

Anyway, as time went on, these effects became better understood. Delta wings were developed in the 50s, along with supercritical airfoils and the area rule. These expanded the tools in the supersonic aircraft toolbox, as it were.

Anyway, the Arrow wasn't pioneering the supersonic interceptor aircraft role. The English Electric Lightening, which was already flying during the Arrow's development, was capable of cruising at Mach 2. While it didn't have delta wings, it did feature the heavily swept wings that help supersonic performance. And the F-101 came out around the same time as the Lightening, and it similarly featured swept wings. It was supersonic, not quite as fast, but had much longer range.

But right around the same time as the Arrow the F-106 was introduced. It was supersonic, with delta wings. It could cruise at Mach 2.3, and had a combat range of 1,800 miles, with other specs comparable with the Arrow. You can see how it incorporated aerodynamic developments. Have a look at this pic. See how the fuselage is bowed in where the wings are? That's the area rule, where rapid changes in cross-section are avoided by reducing the cross-section of the fuselage where the wings are. Importantly, it was the last interceptor the US made--the role was largely made obselete when the threat of bombers was replaced with missiles.

Looking around, the main development seems to have been the fly-by-wire system. The Arrow was the first production craft to use it. However, they didn't invent it--these systems had been tested for decades. While their development is critical for modern aviation (modern aerodynamics coupled with stealth technology can make it impossible to control modern military aircraft with conventional methods), it was on the way already--it just took some time for it to be implemented.

So in summary, it was one of several supersonic interceptor aircraft developed during the 1950s. In that, it was on the forefront of technology, but not ahead of it. The basic concept was one being used in all sorts of planes. While it did have the significant implementation of fly-by-wire, it was the first to implement existing technology. That's really where the ahead-of-its-time stuff comes in. As for its performance, it's impossible to know how it would've flown without more test information.

tl;dr it had the significant development of fly-by-wire technology, which had already been developed but wasn't implemented in other aircraft. The basic supersonic design principles weren't unique in its era.