I have to agree that the reunification of North America's two open-wheel race series is a good thing. The split has undoubtedly hurt the sport. See
this Autoweek article for more details.
Let's see now --- Hmmm, who are the winners and who are the losers? I would argue that there are no winners. Tony George hoped to create a series that ran exclusively on ovals, that was inexpensive to run, and showcased American drivers. The IRL started that way but in the last few years has morphed into exactly what CART used to be. More Brazilian drivers, more road courses, and the costs have skyrocketed.
CART went out of business and was abandoned by all except Newman-Hass and Forsythe. It struggled along and was supported mainly by rich guys, not advertising and that's not a good business model. The new Champ Car had great cars and drivers but was forced to drive in some strange places. There were plans to drive in Korea and China. They raced in the Netherlands.
And the biggest losers of all were the fans. Like a child of parents involved in a bitter divorce, fans were forced to take sides and turn their backs on teams and drivers they may have been fond of. Fans who loved the Indy 500 were forced to watch it made into a farce.
It appears that although reunification has happened after all these years, nobody won, everybody lost. But now the best days of open wheel racing is ahead.