no i've never been to it, but it's literally a race track, mixed with some dark ride in it. on whole it shouldn't be that impressive. the whole Radiator Springs town adds to it because it's themed very accurately. Cars isn't even a very beloved Pixar movie, Carsland was a gamble that was played very well because of the themeing and making an attraction similar to the Autopia speedway.
now does it look cool, with how well they've themed it? yes, personally i liked the movie and i think they brought it to life very well. do i think the concept for RSR is cool? yes, i like fast rides. do i think such concepts are the best thing ever? no. literally it's just a small town with maybe one or two kiddie attractions and another Test Track-esque major attraction. ooh so much better than anything Disney could ever come up with. RSR isn't a new ride physically, but the idea was different than what Disney was doing, and i'll grant them that it's a cool idea, and it came at a time when Disneyland was dead for the most part. Carsland was something DLR needed.
while i don't believe it's the best by Disney in America, i think it's the best thing for Disneyland. i mean come on, it brought interest back to the resort, guests flocked to it. hell i even want to see it for myself whenever i go back to DLR, people loved it. and yes personally i find Indy better, but i'd have to experience Carsland for myself before actually saying it.
and another thing, i really don't like everyone in general just throwing hate at WDW and automatically choosing DLR. WDW isn't perfect, you'd have to be naive to think it is. MK needs updating period, MGM is drop dead boring, DAK needs to sort out a balance between wildlife and actual theme park attractions, the only fair park is Epcot and even then it has its own flaws. but people idolize DLR like it can do no wrong, like its this pristine cornerstone of perfection which is complete bs. both DLR and DCA are extremely small, and before you throw "quality over quantity" in my face, yes size matters. everything is crammed in that resort, there is little room to fit anything. i was surprised they were able to fit in Carsland even. quantity may not make something better, but it can still affect its quality. Disney World is not the best thing ever. but neither is DLR. people jump on the Disneyland adoration train when they don't like what's going on with Disney World, which is stupid tbqh. MK may not be the spitting image of gold but it's a million times better than its counterpart. the only thing i love over WDW is DCA, because its theme is actually amazing. that and DisneySea, two things i wish WDW would look at for inspirations in not only their own parks but also if they ever plan on making another one.
end rant, but basically RSR is neither a new concept nor is it the best concept Disney has made for America either.