I didn't play this when it was all the hype, but even after all these years it holds up really well.
The driving feels great and the progression is well done. A big plus for me was that you didn't have to complete all the events per rival to advance the story.
Seems like they pretty much addressed all the issues that Underground 1 & 2 had.

I ended up playing this like Midnight Club 2 where I just used the cars I'd won through pink slips. Lots of fun and I can see why it gets so much praise.