If it helps, I once tried the Halo spark plug. A salesman for the company came onto the performance forum I post on looking to hawk some. When there were no takers, he offered to send someone a free set to try, and he had the bad luck to accept me as a test buggy. With no other changes to my driving in a 2000 S10 Blazer 2dr 2WD I lost about 3MPG, started having drivability problems and wasn't as fast as it was with regular copper plugs. And boy did he get a review! First he said that my driving style (80MPH everywhere) was why his plugs didn't improve mileage, but then I also posted that putting a set of standard plugs returned my mileage and power, and the drivability problems disappeared. He disappeared, too. I did send him the plugs back though, since they were for testing only.
The problem is, the little spark doesn't turn into a large ball of fire that expands outward, the spark goes from the tip to the electrode, and ignites the fuel to the sides. All the round electrode did was cause the spark to hit in different places rather than one place, which means it had an irregular spark.
On this little mod, considering the electrode wears a little bit with every spark, it won't take long unti it cuts the tip off. A better plug mod is to cut the tip sides down, making a more pointed element to better control where the spark hits. This does not cut off a huge part of the tip, but does mean the plug will wear faster.